300 swap for gas mileage?
 

I have a 1976 f150 4x4 with a 360 NP435 4spd with 3.55 gears. I get about 8 to 9 MPG just using it on the farm but I really want to make it a DD so a 300 sounded like a good motor.
I understand that these trucks have all the aerodynamic engineering of a brick but I wanted to know what kind of MPG guys get with 300's in 4x4s. The 300 that would be swapped in is out of a 1966 M250 Tremec 4sp with no bellhousing and is probably just getting a deck+rings+hone to clean up the bores and true up the block. It doesn't have much of a ridge on it and made good compression when it was pulled a decade ago so I figure its fine but are there any cheap ways to gain power/economy? Are the heads the weak link or is the 1v carb the biggest restriction? I plan to port the heads for a little more flow but the more I look at it the less I want to port something that restricted.
Ultimately I'm just looking for more MPG, parts availability and want to match the 360's power is this unreasonable to expect from a mild 300 with a stock cam?

F-250 Restorer would be your main guy to ask, since he swapped the 360 out of his truck for a built up 300!

But with your gearing and transmission, you should be able to get an honest 14 - 16mpg (maybe more) with a 300. When mine was stock, I used to be able to get 22 with my 1bbl 4x4 300.

The head, intake, and exhaust are all very restrictive and addressing all three will wake the 300 up very quickly. There's lots of posts to the point of redundancy about performance mods for the 300 here. Plenty of reading with a quick search. Four barrel upgrades, exhaust upgrades, head porting, etc.

Have fun, and of course, take pictures.

Oops, you had a 390, not a 360. =X

I thought it was the other way around...50% more power, with the same or better mpg.