I put in a gearvendors OD last winter , so far I have to say it was well worth it

BigBlockMopar said
What kind of ratio's does the GV have and what speeds are you driving normally?
Reason for asking is I have a installed a A518 OD in my '73 Dart and don't come close to the rpm you are still running on the highway, even with my 3.91 gears in the rearaxle.

They have a pretty high ratio for the overdrive, .78 to 1. They do have their advantages, but the leave you with a very short driveline and some potential problems for obtaining the correct driveline angle.

I've driven a B-body with one hooked to a 727, but it just wasn't for me. That particular car had driveline vibration and the overdrive just didn't drop the RPM enough for my tastes.

They are strong though.