4.3l vs. 5.7l in a commuter truck

[JCampbell]

Just thinking out loud, so to speak. I recently picked up an ’84 short bed to drive back and forth to work in (60 miles round trip). It currently has a carb’d 305 that runs like feces. Instead of screwing around with the computer controlled Quadrajet, I’ve decided to swap in a TBI engine from another truck. My default was to source a 350 from another donor truck, but I got to thinking about a 4.3l out of an Astro or S-10.

My question is two fold:

1. For those of you that have a 4.3, how do you like it? We had an Astro a few years back that got around pretty good, but I don’t really know how that would translate into a truck. I’m assuming the curb weight is about the same.

2. What kind of mileage could one expect form a 4.3l/700R4/10 bolt w/ 3.08s? How would it compare to a 350/700R4/10 bolt w/ 3.08s? I’ve read that while 20mpg (highway) is not unheard of with the 350, 14-15 is a more realistic figure.

What I’m looking for is a truck that has a reasonable amount of power (able to get out of it’s own way), gets reasonable fuel mileage (anywhere from 14-20+ mpg) and is relatively easy to maintain (TBI).

What I don’t want is a dragster that gets crap fuel mileage numbers (-12 mpg) that is a constant maintenance issue (carb).

It’s not a tow rig and it’s not a hot rod. For all intents and purposes, it’s a commuter vehicle with a trunk.

Converting to TBI is not the issue here. The issue is what displacement will yield the best results.

Any thoughts?

Frame of reference: