I run 38s under my 1990 truck with kit body. I got rid of the tbi and th400. it is a bi difference. I am only seeing 14.8 mpg average but my truck is a brick and a half and running bias plymudders. it is really light though.

I hope get better mpg when i switch to radials with a higher psi.

still going to be running 38.5s though.