Where to buy a 727 transmission
#1 Stop buying crap off the shelf converters..
#2 Get a quality 9.5" unit from PTC, Dynamic, Turbo action etc. Made to YOUR specs. $475-625.
I don't understand why people spend thousands on engines then refuse get THE most important piece of the drive train quality measured.. It's a HUGE deal to get the most from your combination..
You shoot yourself in the foot every time you don't.