So I'm doing a 6.0/4l80 swap in the 72. Tires are 26" tall, and I can't decide on which gear ratio would be the best for the Ole girl. 8.2 axle. Should be getting the diff fully rebuilt next week. I was thinking 3.73, but not sure. It'll be a cruiser and just for fun, not a track build.

 

If its the original rear end it should be the 8.5" corporate ten bolt rather than 8.2. With the overdrive I would think you could run some lower rear gears and still be drivable on the highway. Sorry I don't have experience with this to suggest a specific ratio.

 

That transmission has a 0.75:1 overdrive ratio, so multiplying that times the rear gear ratio gives the final drive ratio.

3.42 x .75 = 2.56
3.73 x .75 = 2.80
4.11 x .75 = 3.08

All the above final drive ratios were considered “highway gears” back in the day and were used on regular daily driver cars, so I would think any if them would work well. I would go with 3.73 or lower rear gears, personally.

 

^ I would run 3.73 or lower also.
Take advantage of that overdrive.

 

Depends on where you will be driving more. Figure that out and then make your choice. I have a 454 Chevy big block in My Monte SS 1971 and 26.5" rear wheels. I have 3.55 in the car. Then went to 3.73 for 2 years and ran .40 quicker on my et 12.54 et BUT I did not like the RPMs on the freeway as I got use to the 3.55 cruise at 75 80 mph.... I do not know where you are BUT these are normal speed in Ohio now. So for the quicker time which I do not hi9t the track but a few times a year now with it. I enjoy driving the car and the cam is on the smaller side for most peoples engines these days. HMV 272 Crane cam (520 lift square 216 duration) Hydraulic flat tap. 2.06 x 1.72 stock GM iron heads performer intake 750 holley. So for me more cruising. Plenty of burn out power with 2000 stall - BUT I also have a few race cars so I really do not need to feel a race car on the street. Just not comparable so why try.
You really should tailor your car as to what you will be doing the most of and what will make you personally happy.