[fleetsidelarry]

For years, I drove my '66 (with a th375) with what I would have sworn was a 4:11 because of how wound up it was at 55, when I checked it, it turned out to be a 3:73. So, as Captainfab suggested, you might want to find out what you have as a starting point. You can also check the ratio without removing the cover.

I now have a 3:08 (or is that 3:07) with my 700r and couldn't be happier. Around town I can keep it in 3rd (which is 1:1 remember) for anything up to 45 (about 2000 rpm), on the highway 4th (OD) is perfect and, when I want to keep up with the Interstate bunch, I reach down and throw the manual lockup switch. The 700r's low first gear gets you launched just fine, I can still light up a tire if I want BUT, of course, it doesn't accelerate like a 3:73.

BTW, the 71-72 rears ARE 5 bolt