The easy way is using this:
http://www.classicchevy5speed.com/68..._Selection.htm
If you wan't to do it on your own, I'm not sure a T-5 is a good choice with 500 HP. I don't think it will take the torque of a blown motor. However, if you find the right 5-speed, here's what you need.
You might want to buy a Haynes manual for the car. It will show all the parts.
Find a standard trans Nova in a junkyard somewhere. You'll need the clutch pedal and all linkage from the pedal to the fork. In addition, you'll need:
-A manual trans bellhousing. With higher horsepower, you might consider a blow-proof housing like a Lakewood.
-A good performance clutch (McLeod, Centerforce, Zoom, etc.) If you buy a clutch set, you'll get the pressure plate, clutch disk, pilot bearing, throwout bearing and alignment tool in one package. You'll need all of those parts anyhow.
- A good steel flywheel. You might consider getting one with the clutch set, from the same manufacturer. Some folks might recommend a lightweight aluminum flywheel. With your horsepower, I don't think it's necessary.
You'll probably have to have the drifeshaft shortened. Any good driveline shop can do that for you. You may also need a different yoke on the front. I don't know what the T-5 takes.
There may be a ready-made trans crossmember for a T-5 in a Nova. If not, you can probably find a universal and fab it in.
You'll need a floor shifter for the trans, and will definitely have to do some cutting and fabrication on the floor pan.
This change is mostly a wrenching project - but it takes some fabrication.
You also might want to wander around on this forum:
http://stevesnovasite.com/forums/sho...332#post373332