I have done this, as my Dart got quicker the parts attrition got worse. 60' 1.39/1.40 normally now, 3375lbs Nod 489 case, 35 spline, magic pink goo shock proof oil, back braced. I run a 4.30 gear which is probably the worst but it is what the car wants.

I race often it got down to 2 ring and pinions a year, Richmond, Motive, Yukon had them all. I did a 9" and am very happy with it. You will be money ahead in the long run to just upgrade to a tow truck rear or a 9"

I had to type this out 3 times to remove the cutting sarcasm, cuss words, and bad attitude I have on this subject