Yeah heres my advice on that: don't. Complete waste of time. The stock auto trans started slipping clutches at about 8 PSI. Even at 5 PSI, it was just a matter of time.
You are correct. We are about to pull the auto trans out and put the 5 speed in this weekend. We being HillBillyDMC here and myself. We did all the 5 speed upgrades that you did, Henrik. Some suspension upgrades too to include the billet aluminum LCAs and polyurethane bushings from DMCNW. I wont derail this thread anymore than that.
I do have a completely unused master gasket kit for the 3 speed auto by a company named Aldo they sell kits that are on par with modern GM transmission components. Once we did that to my auto trans, one of the metal pressure drums cracked, and that was it for me. Converting to 5 speed manual and never looking back. We guesstimate one more month and itll be ready for a test drive. That is, if we dont have any "oh shit" moments.....