65 manual transmission swap question

My 65 pony has a 200ci and a 3spd non-sync transmission. I want to do a swap for a newer 5spd. I'm thinking of later down the road, putting in a V8, but not sure. What would be the best option for my actual engine and what would by my opcion If I do decide later to upgrade to a V8.

Your input will be appreciated  

would go with the T5 upgrade, with minor mods to it, you can still use the original clutch linkage by removing the standard fork for the T5, and using the fork you already have and fulcrum, then raise it up using a 3/4 by 3/4 by 1 1/2 block, have pics as to wherew the block goes and drill the holes through the bell housing, Then just have to get the rear tranmission support, and the drive shaft shortened, and balanced.  

Hi,
I did a C4 to T5 conversion a few years ago. Your project is much much simpler. Ina any case contact one of the popular vendors (Modern Driveline/Keisler Engineering) for kit advice. Basically, you'll want to R&R the clutch/pressure plate, T/O, and pilot bearing. You'll need an adapter plate to mate the T5 bolt pattern to your bell, as well as, add the distant needed to accommodate the longer input shaft of the T5. You may or may not have to shorten your drive shaft (I didn't). Since you're a 6 cyl., I'd opt for acquiring all of the parts first then do the whole conversion at one time. Also, know, you'll need a spring and hub change, as well.
BTW, I started with a V8 and bought all new or NOS parts.
Good Luck with your project.  
Ken
RestoMod 64.5 Mustang cvt.