Don't be afraid to go with a truck engine as they are cheaper and plentiful, and have great heads so a cam swap really wakes them up.
However, as much of a Gen III/IV proponent as I am, it's always bothered me that they don't sound "right" in the old hot rods due to their firing order. And though I think carburetors work on voodoo, again the old cars look better when you pop the hood and there's a big round air cleaner on top.
Having said all that, for my money I'd probably swap in a late-model fuel injected engine. I thought through this for my old truck, and the hp/dollar is hard to beat when comparing a takeout 5.3 (with cam upgrade) or LS1 to a 350+hp old school carb setup. Not to mention driveability and fuel economy. But I also realize they don't just drop right in; you have to do a little fab work for motor mounts and maybe trans mount, plus all the considerations for electronics (though all these things are available in well designed kits these days).
It's a tough call, and I guess your skill level and how you plan to use the car are the deciding factors. Oh yeah, and $$$.