Beginner Road Racing: Transmission Question for Budget and Angry Knee

I've been to (I think) 5 track day events so far with my '70 Duster that has an A-904 with a shift kit. I basically don't downshift to 1st until I'm accelerating out of a corner otherwise it'll unsettle the rear end (at best) and I worry about burning up the low-reverse band and 1st-gear clutches. I think the only reason it's still alive is that I'm running a big aux cooler (about 10" square iirc, put it in about 12 years ago lol) and deep cast pan. I honestly hate having an auto in that car, by far the biggest issue I have with it. Some day it'll get a TKX 5-speed but until then I'll just have to live with the lack of control and rev-matching of an old hydraulic-controlled 3-speed.

If I was going to keep it auto, I'd skip the Torqueflites and run an 8HP70. That's the only way you'd be able to have something that can work well in a road racing environment. Torqueflites are great for drag racing (or pushing around a street cruiser or truck) but they just flat-out suck for long-duration, high-intensity racing with lots of downshifting.