Auto to 5 speed in my 65 pickup?

The turbo400 in my beater project truck is due for a rebuild.its a 65 gmc 1/2t with a 350chevy engine. i've been toying around with the idea of swapping it out for either a th350 or if i can afford, a 700r4 or 200r4. Main reasons are horrible hp loss of the big th400, and lack of overdrive. i started thinking, wouldnt it be cool to swap in a late model OD manual from a salvage vehicle and adapting it to the old truck! I'd get more power to the ground than any auto,benefits of overdrive and the fun of rowing thru the gears!
 So my question is, what vehicle would be a good candidate for a swap?  Car or truck? Horsepower would be in the 3-400 range. No towing so car parts should hold up. I was thinking either a 90's Camaro or Silverado if i went truck. whatever i'd get i would be robbing the whole driveline basically and fabbing it in. clutch assembly driveshaft crossmembers etc. more stuff i can use off the late model the better.
 Any ideas on this? i know its alot more work than an OD auto but worth here. thanks in advance.  

There are 4 main issues that I see.  First of all I would stick with your current engine as it likely runs.  If you put in a late-model engine you have the hassles of the ECM, wiring etc.  As far as a straight tranny swap goes the first issue is the clutch.  This can be solved by using a hydraulic clutch and robbing the clutch pedal from the donor.  Mounting may be an issue so check it out.  The next issue is the hole in the floor.  Not too tough but it will hack up the truck.  There are plenty of shifter boots around - make sure the one you get is waterproof.  The next issue is the crossmember.  Someone probably makes one or you can find one that fits.  Make sure you get the cross member off of the donor car in case you have to make one - you can cut the mount off or possibly modify the donor to fit.  The last issue is the driveshaft.  Make sure you get the donor driveshaft and tranny yoke.   You will most likely have to have a driveshaft fabricated.  This one is really easy but it takes money (a couple of hundred bucks).  Don't even think of trying to make one yourself unless you have the proper tools and knowledge.  Actually there is one last issue and that it the location of the shifter in the tranny hump.  You need to make sure that the shifter doesn't interfere with the dash or the seat. I'm assuming that you will be pulling the trans from a donor that has the same bell housing pattern as your engine.  Good luck!