OK so it looks like I got my rear end squared away for a lot more than I thought lol! So now I guess I’m going to buy myself another Christmas present.
I’m looking at the Tremec five speed transmission along with a hydraulic clutch kit. They say it is a direct replacement and a friend of mine thinks it’s fantastic. Just want to hear from anybody if they had any experiences, igood or bad with doing this conversion, I would love to hear any tips and if there’s anything I need to look out for. Looks like I will be meeting this to a 428.

Did the tremec 5 speed in my 69 400 4speed 2 years ago. Very happy, great with overdrive on the freeway, Of course I kept my m21 as it is numbers matching. Go for it you will be happy

Glad to hear your recommendation! Another Firebird enthusiast John down in San Diego, who has helped me out considerably. Also has done it and loves it! I’m going with 350 gears in my new rear end and the 0.71 overdrive. My car was all original, it was a one owner that I bought in an auction in Oregon 10 or so years ago issue I had when I submitted everything to PHS. It wasn’t documented so it really didn’t matter so I decided to make a lot of changes, unfortunately before I found this out, I did sell a numbers matching coupe that I had bought off an Indian reservation in Bishop California That went to somebody I believe in Montana. Can’t wait to try everything! Big issue I have right now is I can’t get aluminum heads for about three months so I can’t complete my engine.