1977 van stock MPG

Does anyone know what kind of MPG a 1977 chevy shortbed van with a 350 and auto trans would get. Pretty sure it is a stock motor.Don't know what auto, and I am a easy driver. Just a round about figure. Also would a later model 350 tuned port motor adapt in place and do any better ? I am curious because it has a 4X4 unit under it and I know it will get worse MPG but want a idea of where it was when stock.

Thanks for the help

A 350 in a 3rd gen wigth no overdrive would probably get about 11 or 12 mpg. A tuned port injected 350 with an overdrive trans would probably be a little better. Also depends on your rear gearing, tire size and how fast you drive.

I have a 1972 Chevy shorty van & with my old 305/Turbo 350 auto trans was getting 12 on the highway. It has 3:40 rear gears.
I was getting 12 even when I swapped in the 454 big block.
I now have a 330 horse 350 in it & get around 8-9. Brad

thanks for the replys, not sure if I want to go this route or change a 62 ford with a IL6 to 4X4.