56srw, my street rod is a 350 sbc powered '32 Ford roadster with a mild Crane cam 218*/230* @.050 and a 2004R trans (.67 OD). It was a dog in OD even at highway speeds with 3.40 gears. With 3.80 gears it pulls all the gears well and gets a best of 20 MPG on the highway, much better than with 3.40 gears.
After 15,000 miles of test and tune I don't think I will be able to get 21 MPG out of it with my skills.
