Change the rear end.

[Fran Blacker]

4:10 and a 31 inch tall tire

Your car and gas milage!

 

[blue69runner]

Thanks Runcharger. Have a 489 to build and put in. So think I will try that combo.

 

[HEMI-ITIS]

Your car and gas milage!

I can pull almost 10 MPG if I stay out of the throttle

 

[66Satellite47]

Gee, 7.5 MPG with a 383 indicates it needs some serious tuning or your foot is in it all the time.
My '70 Barracuda did a 12.5 -13.5 with the stock 2bbl (piece of junk). Switched to a DP4B & 3310-1 Holley gained 1-2 MPG and a bunch of power.

 

[Longknife]

I am wanting to do just the opposite, I have 323's in my RR and want to go to 355's. I am considering 3.73's too, The Hell with mileage, I want to have fun!!!!!

 

[Longknife]

This is fun to play with,,,,
http://wallaceracing.com/calc-gear-tire-rpm-mph.php

 

[Outlawd]

Sometimes you just find that sweet spot by small changes, I went from 3.73's to 3.23's on my Coronet and it made a world of difference in town and on the highway. Changing street rpm's by changing tire size also changes you cars look, it might be cheeper and easier but not the look your after. I lost about 600 to 700 rpm at 60, don't sound like much but that's huge with a blower on top. Less rpm=less boost=less heat plus the motor just sounds happy at that cruising rpm. Your probably looking at dropping around 300 rpm's in your case, don't seem like much but could be just enough, when you find that sweet spot you will know it.