[low63gp]

Gentlemen,

I have replaced the tired 389/Slim Jim with a 455-TH400 in my 62 GP. Now my speedo is off by about 15 MPH at 55 and she really twists up on the freeway just cruising the speed limit. It seems the TH 400 has a lower final gear ratio than the slim jim?

If that's the case I would like to change rear end gearing to solve the problem. I read that 62 GP came with a 3.23 for A/T. So if the above is the case, what rear ends are available (if I could find one) for my car, I would like the highest available as I do a lot of long distance freeway driving. BTW I'm only looking for an open rear end.

Thanks,
Mike