I think it really depends on what you want. For sure fuel injection is great, but is it worth it to you? I just completed a proformance unlimited 383 swap and so far it is great. The carb is fine, very responsive, and as I don't plan on any cold weather here in Tucson, az it seemed like a great way to put that 2k back into the body work while still having a motor that I love.

I would not at all even consider a BB, you will run deep into the 12-16K range to do it correctly and its just not worth it. There are some great 350 crates from GM, or any of the legit performance type buliders. The legit ones have been around for years and offer some great warranties as well. To be honest, there is part of me that wishes I would have gotten a little less powerful motor and made it more streetable and smooth.l

Just like another poster said, the TPI units from wrecked cars would work just fine if configured for what you've got and what you want.

 

i have looked at many big block set ups in 2nd gen unibodies and almost everytime, the body is twisted, some a lot more noticable than others. its less likely to happen with an enjoyable small block that is streetable as djs383 said.

 

The sbc 350 is a well known workhorse. Tried and true. If you want fuel injection then a kit would definitely be cheaper than replacing the entire engine.
Holley TBI kit:
http://www.summitracing.com/parts/HLY-950-24S/

That's a moderately priced fuel injection kit, but it wont bolt directly to your carburetor intake manifold. You can either spring for a new manifold or go with a converter plate.
TB to Carb intake plate:
http://www.summitracing.com/parts/PRF-60118/

or EFI Manifold and fuel rails:
http://www.summitracing.com/parts/EDL-7137/
http://www.summitracing.com/parts/EDL-3630/

and @ breakstuff6290:
I do agree what you and djs383 said about sbcs being smoother and more streetable, but the warping is because the people didn't install sub-frame connectors before they "dumped the clutch" for the first time. And a well tuned small block can warp the frame just as easily as a big block. =)

 

wow 2nd gen dan, i never thought about subframe connectors. im gonna go order me a pair right now and drop in my 427 tall deck. its gonna be awesome. thanks.

 

No problem. They helped me out a lot with mine. That and a new set of bushings actually straightened out my body. Good luck with the 427.