I am new to this forum and I have a question. I have a '65 Mustang, bought new, with approx 240K miles. I just rebuilt the front suspension and manual steering with all new parts with the exception of the steering box which I didn't touch.  The steering is very tight and stiff now even after having it professionally aligned.  The alignment shop said it should loosen up in time, but after several weeks I notice no change.  Any ideas as to the problem?  Thanks.  

First get a second opinion from another alignment shop. Never heard of steering having to loosen up other then from parts wearing out. I also have a 65 with manual steering and did the entire front end, replacing all parts that had excessive wear. Didn't notice any change in stiffness. I also took out the steering box, dissasembled it, inspected all parts for pitting etc and only found one bearing needed replacement(expensive). After putting it back together, filling with lube and adjusting to take out steering wheel play it works fine. If your car has 240K the steering box should need a rebuild or at least an inspection. If it worked good before don't see any reason for it to stiffen the steering though. Only the idler arm and bushing (if replaced) would add some stiffness as the rest of the componets move on the ball joints. Finally Mustang manual steering is manual labor and worse if you have gone to bigger tire sizes. I'm in the process of converting to power steering and front disc brakes to solve steering and braking concerns. Trust the above provides some help.  

Appreciate the response.  The steering box probably does need a rebuild but I agree, that if it wasn't stiff before, and I didn't touch the box, it's hard to see how it's the culprit.  I did replace the idler arm and was thinking that that could be the problem.  I may put the old one back on just to check that possibility. The old one wasn't bad, I just replaced everything while I was at it.  Thanks again.  

I'd start isolating components as in disconnecting pitman arm from linkage(and so on) to see exactly where the stiffness is coming from.