12v MPG in a 3400mpg vehicle

[BLACKJACK]

I am doing a swap into a 54 Dodge pickup.
I have a 12v that needs rebuild. I’m curious if anyone might have a guess at what kind of mileage, as a best case scenario, a person can expect (mostly highway) in a light 2wd truck.

Assuming that I choose the right rear ended gear and transmission and that a person is staying out of the throttle and driving it like an old person.

 

[BLACKJACK]

I guess I can’t change the title. That was supposed to read 3400lbs not MPG.

 

[Cummins12V98]

Stick with 3.55's freeway a solid 25mpg.

 

[BigPapa]

I get 19-21 in my QC SB auto 3.54 with regular daily driving. On empty highway trips @ 70-75mph I get 22-23.

 

[AnonEd]

Don't forget the '54 might not be as aero as Bigpapa's and Cummins12V98's newer trucks so speed will drop mpg faster. A guy I met with a 215hp spec 12-valve, tall-geared Rat Rod with virtually no aero benefits (like bodywork ahead of the cab) said he did 25-27 all the time.