Swapping my LG4 for another V8 this summer.
Background:
Bought a straight, rust free 85 Z28 with 75k on it last summer for $3400, that was originally silver, but the original owner had it redone in red. I got custom plates "BMB PRF" 'cause thats what I want the car to be one finished, bombproof. I'm taking it back to the original silver, but with graphite-coloured GFX, with 17" ZR1's. Pulled the complete grey interior for a 1LE AC delete dash, 4th gen seats custom covered, and black panels, and yanked the AC off my LG4. Trying to go completely mechanical on this car, with none of that electronic whizz-bangery, in keeping with the "bombproof theme. 4 speed700r4, with a 10 bolt, 3.73 posi rear end. Gonna go with a complete Spohn chassis upgrade.
Question:
While trying to keep close to 1 hp per cubic inch, whats the best block size/top end combo for fuel efficiency, as this is gong to be a cruising car, and given the price of gas, I'd like to actually be able to afford to drive it to shows.
I've got a possible hook-up on a #'s matching 327 out of a Vette, that my buddy is swapping a 427 in for. Anything I could do with that?

 

Depends on what you mean by bomb proof. Keeping the 700R4 and 10 bolt won't make it bomb proof.

You want an engine that will last forever? Get a low reving engine. Keep it under 4000 rpm but then you'll never get that 1 HP/CID.

 

The stock engine rarely sees the high side of 3000 rpm, now as Im not a leadfoot. Looking for a strong setup that does all the good stuff under 5000 rpm for AutoX. Maybe add a 75-100 shot later for some strightline fun, without compromising fuel economy.

 

Whatever displacement, I'll probably go with an Edelbrock 650 non-egr performer carb, and an air gap intake. Vortec heads are a thought I've been kicking around too. Are they good for bottom end power? One would thinkso, since they're on all the truck engines.

 

An Edelbrock carb would be a downgrade from what you've got now - worse fuel economy, and not a lick more power.

The 305 is a decent choice for your primary goals. Vortec heads shaved to 58cc, Vortec Performer intake manifold, all new exhaust starting with headers and none of it listed for the LG4 application, cam upgrade (keep it roller lifter), dual snorkel air cleaner, and the rest off of your LG4, you'll have power you never thought possible while maintaining decent economy.

If you want to do better than that, get an LS1.