Best combo for fuel mileage?

[JQ-72]

I'm looking to get my 1968 swb truck on the road as a possible daily driver for a while. I'm either going to run the original 307 V8 or possibly a 250 inline 6. Trans will either be original TH400 or 700R. I have a 3.08 or 3.73 rear axle available. From the above, what would be the best recipe for optimum gas mileage. I drive about 30 miles a day round trip to work in a 45 MPH zone. Thanks for any help.
Joshua

[trac209]

I'd Go with the 700r and the 307 and either gear ratio would be fine. The lower 1st of the 700r will help get you rolling with the 3.08 gears. While the 3.73 would give you some extra pull on the low end.

[TwoFiftyShifter]

Its going to be the 700R with 3.73 gears. That was the standard MPG benchmark from the early 80s until 2007 or so. That is the combo. Either motor, really.

[hugger6933]

I'd go 307 700r4, and 3:73. I think you would be very happy with that and if you decided to up it a little a 350 in front of the 700 and the 3:73 would be a really great combo. Jim

[creekncabin]

I am running a 350 2bbl, TH350 on a C20 long bed. Unsure what my rear end gears are yet. I have been getting 18mpg regularly. Put 105 miles on "Cold Ethyl" yesterday and 5.75gal of gas this morning.

[Fitz]

Big block, 4 speed, 4.10 rear!

[R.L.]

I'm running a 250 w a 3 speed std and I'm only getting 12-14 mpg. I was told a couple years ago the little motor wouldn't net much in savings due to the fact it has to work harder to get up to speed than a 8 does and that seems to be true, I only went with the 6 to be different and well I'm use to them from other older stock trucks. What the best tire rearend combo for my application is I have no idea I just know I don't have it at this time, LOL.

[TwoFiftyShifter]

I used to get 15 MPG in town with a SWB truck, it had a worn 235 with 3.90 gears. I think of is on the highway where the I6 struggles with MPG.

[FLDBRED]

Originally Posted by JQ-72

I'm looking to get my 1968 swb truck on the road as a possible daily driver for a while. I'm either going to run the original 307 V8 or possibly a 250 inline 6. Trans will either be original TH400 or 700R. I have a 3.08 or 3.73 rear axle available. From the above, what would be the best recipe for optimum gas mileage. I drive about 30 miles a day round trip to work in a 45 MPH zone. Thanks for any help.
Joshua

I would go with the 307 with the 700r4 and 3.73 gears. It looks like with the 45 MPH zone, the 3.08 would be a little tall with the overdrive trans.
I would go with an Edlebrock performer and small 500cfm holley anf HEI ignition. The ram horns will be fine with a good dual exhaust.

[68Gold/white]

Many ways of thinking...
Heavy pickups need torque, just to keep them moving. Smaller engines have adequate power to move them around, sounds easy, but you need at least 350 cubes to move them around EASIER...
The idea of driving down the road at 70MPH w/ engine turning approx. 1800-2000 RPM's is the ideal situation for better MPG, it's just not easy on a smaller engine like a 307 or 283, they lack the torque to do the job easily, those smaller engines would move your pickup at those RPM's, but struggle MPG wise because they'd use as much gas or more trying to keep your vehicle moving...it would be a struggle, understand...I've been here, done this....

What are your MPG expectations??? Don't get them too high. 12-16 MPG for one of these old heavy pickups is a pretty good #, some have done better, I know.

Driving on the 45 MPH road will help your deal. I'd use the 307, a 2101 performer intake w/ an edelbrock AVS carb. The AVS is the air valve secondary carb, much better than the 1406 AFB that every parts store sells, a little higher $$$ wise, but much better to use, especially on a smaller engine. They make a 500 CFM version that would work on the 307 well. It doesn't matter if you use headers or stock exh manifolds on the 307, the engine isn't big enough cube wise for the headers to help.