Mine 71 GMC swb w/ a stock 250 6 cyl and 3.07 gears pulls down 15 mpg (!) Granted, I am pretty heavy footed with it. I plan to check it again next week or so after I have gone though another tank of gas while driving a little more sedately. After driving this truck a while, I have come to the conclusion that for a daily driver, the little 250 would be hard to beat. It really does have plenty of power. Back in my younger days I would have yanked it for a V8, but it is so smooth that I have grown to appreciate it.
I have pondered swapping a 700r4 and putting the stock 3.73 rear back in. It has good pickup from a dead stop now, it would be great with the 700r4 and 3.73's. I have all of the parts to swap it to auto, even a 700r4 core that the seller said he did not have the TV cable adjusted right after it was rebuilt. There was clutch material in the pan. Hopefully it won't need any hard parts.
We bought a house and are closing on it in December, so it is for sale. It would help us have a bigger down payment if I sold it. All of this could go with it if I got my asking price.
Don't worry... I have plenty of other projects to take the place of this one !
http://67-72chevytrucks.com/vboard/c...m-truck&cat=12