We have been using a borrowed GM powerglide in my granddaughters race car since the end of last season.
It belongs to a member of our racing family and wasn't being used but we hate to use borrowed stuff any longer than needed.
My son found a few powerglides that had been pulled and put in storage 20+ years ago and we brought some of them home!
I started by purchasing a good manual and going to UToob University for about 30 hours.
After getting educated, we ordered a Master rebuild kit and started getting ready.
I built a stand to make working on it easy and built quite a few tools to pull the pump, compress springs in clutch packs and remove/install bushings.
I took my time on this one as it was the first and I built tools specific to the job at hand as I went along and used the internet and UToob if/when a question came up.
Start to finish took about 10 days but there were lots of stops and more specifically, waiting on little parts that were not in the Master rebuild kit specific to performance.
Since I am getting smarter as I get older, I don't like lifting and straining moving stuff (because that kinda stuff tends to hurt) I built a fixture that bolts on side of transmission and allows you to get to everything. It also fits into an engine stand so you can flip it over pretty easily. I added a lift eye to the fixture to make it even easier to deal with. I bolt the fixture to the transmission with 2 bolts and I can move it with my FEL to take outside to wash, etc. and easily install into the engine stand with the engine lift.
I started with a 1970 V8 Powerglide core.
After about 10 days of tweeking, tuning, massaging parts, etc. this is the result.
Since this is a racing transmission that we run in low only and only has to have 1 forward and reverse, the high gear clutch pack internals and govenor that controls automatic shifts was removed and saved 7 pounds of spinning weight and lost lots of drag and heat produced inside the high gear clutch drum while running in low only.
Here is a shot of her making laps on the practice track behind the shop. She has ran 3 seasons in karts and is moving up to full size cars.