Here's another of my 2 cents, um, I mean 2 pence worth......
If you're going to swap engines, why not look into something
modern with multi-point fuel injection, maybe 4 valves/cylinder,
etc. Something with ultra clean emissions and top notch
Why go with a dinosaur? Big and heavy and dirty.
An Olds Quad4 would probably make a nice choice. Or maybe the
Chrysler Turbo 2.2 with intercooler. You'll get similar (and
actually higher) HP, better milage, etc.
For that once in a while type boost, I'd even suggest just
getting a nitrous setup. You'll be blow'n away Vettes with a