I'm not a transmission builder but worked for almost 30 years in the transmission parts and converter business. Most of my information comes from observing and listening to builders that I'd trust with my mothers car. Over the years I watched these builders put everyday and performance transmissions together. They all had one thing in common, they wanted to do them right. One very good builder quit the shop he was working for because the new owner wanted him to take every short cut possible, something that he would not do.
I bought a 74 Challenger back in 2002 from the original owner. It had about 32000 miles on it, and other than taking it out in the driveway once and a while to warm the juices up, it hadn't been on the road for over 20 years. Lots of oil leaks of course from sitting, and when I spoke to the guy that ended up building my trans, I told him just to do a re - seal, he said no way. "It's been sitting for a long time and it should be gone through properly". It was good advise as we found parts inside that would have probably failed sooner than later. Doing a quick re-seal wouldn't have found these issues.
The best advise I can give anyone doing their own or having someone build their transmission is:
DO IT RIGHT --- ONCE
