67 running too hot, help

My 67 fastback; 289 has been running nice and cool since I bought her last August.  Suddenly she's running really hot (but not boiling over), and it feels as if the heater is on, full blast, in the interior.  My garage cannot figure out what's the matter...I am baffled, don't know what to fix?

Here are the facts.
I just installed a a new power steering pump, saginaw style (better with my rack and pinion).. the pulley seems fine, and everything seems to be turning properly.  The water pump seems to be fine.  I just put in new spark plugs. The carburation seems perfect. Idling at 800 rpm.  I also have a new radiator shroud...6 blade fan, and a fairly good radiator.  I did go to the track last weekend for the first time...and pushed everything pretty hard. This is the first time the car has been to the track...so the engine probably was under a lot more stress than usual.  But I did not push much over 5000rpm. The engine seems to be running strong.

Here's what we checked.  
Changed the thermostat to a brand new 160 degree.  
We read the temperature of the motor at different points and water pump with a thermal guage.. The average temperature is about 185°  a bit cooler on the water pump, the temperature reads even on both heads.  There seems to be more heat than before.  The high heat in the interior seems really odd to me (heater switches are off).

If I had a blown head gasket, would there be any symptoms other than heat?
If the radiator was a bit stuffed up, is there a way to tell?  

Your temperatures seem to be fine. It doesnt sound like there is any reason to believe there is blown head gasket. A blown head gasket usually means water in the oil or water in the piston or both or loss of compression. You have no reason to suspect those things it seems. Simply because you changed the thermostat to a 160 degree stat doesnt mean the motor will run at 160 degrees. It just means your stat will be wide open above 160 degrees. Normal operating temp should be somewhere between 180 and 200, track time could increase that. I suspect the problem is that air is leaking past your cowl intake and going thru the heater. The cowl ducts have a shut off that works ,,,,partially well. Its also possible your heater control wires arent set to shut the duct fully. You can remove the ducting from your cowl intakes up under the dash, in the far right and left of the footwell and feel if the ducts are closed. They leak in a lot of mustangs.  

thanks,
I know the engine temps are reasonable, but my car ran really cool until now.  It has the larger ford radiator, the one used for ac cars...and a 6 blade fan.
I am starting to be suspicious of something else.  
When the car is completely cold, it barely runs on 8 cylinders now.  As soon as it warms up it runs better;
but then runs hotter.  I’m now thinking I have an electrical problem.  I have an electronic ignition (petronix).
I just changed the voltage regulator, because I was getting too much, like 15+volts, causing the battery to sizzle after long drives..
now the juice out is fine.  But I think my new problem dates back to about the time I changed the voltage regulator.  Or, we also moved the coil, as we changed the steering pump.  I am wondering if there is something up with the coil, or ignition...is there a reason not to run all cylinders when the engine is cool?
I read another forum, and someone was having similar problems, because of a bad ground, or not enough power to the coil..  Does this seem possible?  

John,
 You're jumping all over the place here!  Engines are designed to fire on ALL cylinders, period.  Rough running while cold is usually a choke/fuel problem, not ignition.  Temperature doesn't effect a coil.
The rough cold running is one issue, heat getting into the interior is another.  You could try by-passing the heater core, and see if that changes anything.
 As MechGuy said look at how well the firewall is sealed from any air infiltration.  You mentioned your radiator is a larger Ford one.  You could have some clogged tubes.  
Has it been flushed in a while?
 Does the interior cool off if your cruising at a steady speed, and heat up more in stop and go traffic?
Are your mufflers too close to the floor?

With rough starting and idling the first thing I'd check is if the choke is properly working.  Make sure it's well lubed to freely close, and then open on temperature rise.  
Be sure to post what you find out the problems were.
Good Luck,  Marc B.  

Marc,
I am jumping, because it's one of those mystery problems.
System is clean.
Mufflers are not in the wrong place.
It heats up in stop and go traffic, and cools down on the highway.
The heat in the interior is a new problem, and has manifested itself at the same time as the running on a few cylinders at startup.  
The choke has been checked.  The car runs well.  
At startup, running rough, it did blow out some strange blackened water.
Is it possible that I have a small head gasket leak?  there are no other signs...  

John,
 This sounds like a tough one to trouble-shoot.
While cold, check the coolant for any signs of oil.
Also check the oil for any signs of coolant.
If a head gasket blows out between cylinders, I think that's when the car spews steam
out the exhaust, as coolant makes its way into the cylinder chambers and burns with the gas.
 The black water may just be condensation buid-up in the mufflers.
The fact that it's black may mean it's running on the rich side.
What CFM is the carb? A stock 289 only needs in the 450 range.  Good Luck,  MB.  

If it heats up in stop and go and cools down in steady highway speeds, then your radiator and adjacent things such as a shroud need replacing or added.  When these old engines were new, they didn't need a lot of water to keep them cool, but as they age and build up calcium deposits, the radiators need to be upgraded to larger and more efficient ones such as an aluminum one.  If nothing else, get that old radiator rodded.  

Thanks soaring...
I will check the radiator...the shroud is new.
The radiator seems to be ok, I think it's not so old.
I'm suspecting there is a problem in the electric choke, or something electric, that's somehow causing the car to run eraticaly. I know this does not make sense, anyone have a clue?  

Running hot and running eratic are two different issues.  Just unplug your electric choke if you think that has something to do with it running erratically, but I doubt that is your problem, and has nothing to do with it running hot.  

Ok...
some things are clearing up....
My mechanic put the system under pressure and nothing seems to leak.  Everything seems to be running fine.  He adjusted the timing a tiny bit, and the carb.  The engine is running tiny bit hotter than before, but is well within norms. no one things there is any sign that it could be the radiator, or head gasket..etc...
the only real problem I'm having still, is that there is a lot of heat in the interior of the car.  The exhaust system is also fine, and in the right place.  and of course the heat is off...but it feels as if it is on????  

Ok...looks like there was not 1 problem.  The engine was running a bit hot...the timing was a bit too advanced, and there was a small exhaust leak where the header is bolted into the H pipe.  The heat in the cabin in traffic, was a small amount of hot from the exhaust, and the engine running a bit hot seemed to be the timing.  Probably my radiator needs a bit of a cleaning too...but I don't think it's too bad.