I can tell you that you will be doing yourself an incredible injustice if you dont put a 396 back in an origional 396 camaro. They are worth so much...
But in camaros, 396's were pigs. They make the front end all sluggish. They car kinda feels like a big tank. 327-400 sbc keeps em nice and light.
My thought is to throw a 396 in that car, make a butt load of money off it. Then go buy another one (not 396 car) and throw a punched out 400 in it!
Only other thing that I would suggest doing is to throw a 427 in that car if you dont care about origional or the money you could make off it.