if the 360 is a good motor, I would probably use it. You'd have more low end torque and power. You may give up a mile or two per gallon... but not if you are pulling.
Apples to apples comparison.
My dad has a w150 extended cab 360 4-speed 3.55 gears 14.5 mpg. He documented every gallon of gas he put in it since new.
I had a w150 318 4-speed 3.55 gear shortbox truck 14.5 mpg.
The 360 is a way better truck engine.
Both trucks are 1978.
