You want a T5 out of a V8 camaro or trans-am to start, one that has a tag to properly identify. 1989 to about 93. These transmissions are what they call world class and has stronger gear sets. To further identify look at the front input shaft left and down a little is the front bearing retainer. If it has some writing on it and it's raised a bit it's a world class, un rebuilt transmission. If this cap is smooth and flush it's a non world class, forget it. Next Identify the o.d. Ratio, do the math to determine compatibility with your rear. I would suggest a professional rebuild to guarantee reliability. Also re-enforced o.d. bearing retainers for sale. T5 od rations are .63, .72, .73, .76, .86. The formula goes like this:
366x 60x rear gear ratio divided by tire size = rpm. (rpm x o.d.) = final rpm. 366 is the constant, 60 is the speed, rear gear ratio divided by tire diameter = rpm in 4th gear. Over drive rpm determined by multiplying this rpm by the o.d. Ratio. ANy of these parameters may be changed except the constant. MAke your self a chart, get out your calculator and have some fun. After a while you'll see the final gear you can live with given the 261 engine and the o.d. you are stuck with. My personal favorite o.d. ratio is .72
