O.d.

I figured on using 1st,2nd @ 3rd for the occasional race but not 4th or,od under power. As far as Why? Simple,,,16 to 20 mpg in a light A body, instead of 8 to 10. The opportunity to drive cross country at highway speeds @ 2000 rpm,also see mileage. I'm not building a garage or trailer queen. I'm partial to mopar. Always was when younger. Gas was .69 cents a gallon then. If I can't create a combo like I want,I'll just sell he car and do something else... But thanks everyone for all the advice. Once my "direction" is figured out,I'll start buyin or sellin stuff.

If you are not going to beat on it I would use the OD box. As long as you don't slam it into 4th (which is ironically, 3rd gear inside the trans!!!!!!!) you will probably never hurt it.

Because of tech increased trans speed when in OD I would use, at a minimum the very best 75w90 100% SYNTHETIC gear oil in. Don't be afraid to put a pint or pint and a half more oil in it. If you can find it, I would use 75w140 gear oil in the trans, as long as it's 100% SYNTHETIC.

You won't hurt it with the higher grade oil.

Keep us posted. I hope you do it.