Whats your 67-72 chevy 2wd or 4wd gettin on fuel millage?

[Sammy]

My 71 GMC SB 96 350 Vortec (about 20 grand on the motor) with 600 Holley n 350 turbo 307 rear 15/16 max on the hwy at 60/65 or below. The 69 LB 350 (65 grand on the motor) w/4 spd top loader and 307 rear is about 2 MPG less depending on how hilly it is. When I had the stock 2 barrel carb on it I could manage 16/17, but not much difference. Any MPH above that results in a drastic reduction in MPG.
Trying to average 20 MPG in one of these trucks as heavy as they are would be difficult to say the least.

[trucks72]

I do not think I could put one together again that would do that. It was just the right combo all around. How good do some of you guys with LS motors get in these trucks?

[292farmer]

i get 12-13mpg with a 292 sm465 and 5.13s...i don't go past 50mph so im sure that helps i did do 60 for a week and it dropped right to 10mpg. im hoping now that i got 4.13s i can get 15, though i'd be happy with 13mpg and 60mph
one thing i will say the fuel mileage doesn't change when i haul or tow anything, im assuming that due to the gears and low end torque but idk.