but your 72 has the transmission with the really low first gear which help it with the big tires. plus AFB's are suppose to get decent gas mileage because of how small the primaries are. i have been thinking of trying one on my 81 buy am slow to get around to it.

 

1st is WAY too low to ever use on the road. Off road crawling/pulling something out of a stuck is the only time it ever sees 1st. It's also my parking brake haha

If I could get that carb to behave a little better on hills it would be perfect. I haven't ever messed with it except to clean in though...

 

Holley's selector also i believe asked about intended usage of the vehicle, if your primary concern is gas mileage you might want a small carb, in fact you might be better off going to a 2 bbl setup, or staying with a rochester, on a 4x4 vehicle thats used mainly offroad a 470 truck avenger carb might be a good bet.

I took the OP's comments to mean he wanted to make more horsepower so my advice was based on that.

Curious to know what kind of carb's are on the 2 trucks you described. My 85 4x4 still has the factory 4 bbl rochester carb and gets over 14 mpg carrying a thousand pound camper

 

my 81 has a Holley 570 street avenger and the 91 has a stock Holley 2 barrel carb. the 570 is a pig on gas and and it is not that powerful but i got it for free and it was smaller than the Holley 850 double pumper that was on it when i bought the truck.

 

I would love to go to a truck avenger in the future, but I had the AFB already, and didn't want to buy a new carburator for the truck. I've only got about $3000 total in the truck, purchase included.

I get much better mileage with my 4bbl than i did with the 2bbl. I have always heard that the right 4bbl will get better than a 2, due to having smaller primaries, and larger secondaries to use when needed, while the 2bbl has to make do with just 2 jets that have to support it while cruising as well as when floored.

 

Crazywofie...holleys are notorious for not being very fuel efficient, I don't know too much about that particular model but was under the impression that if it was jetted and tuned right it could get pretty decent mileage

2x72 what u say might very well be true, I haven't ever run a 2bbl, but spread bore 4 barrels probably get better mileage than square bore models, because of what u described

my truck has a 360 in it and someday its gonna get a 570 avenger