You have the wrong one. There is a 50 OZ imbalance to deal with ie AOD and 5.0 HD in a 65 cvt.
Had the same problem, putting a C-4 trans with the HD 5.0 Buttoned it up and headed across state to put miles on it.Drove it around town first and put about 150 Miles on it.No problem.
Drive across state to Naples, Fl. Never went over 60-65 and varied speed a bit. Np probs!
Upon return, decided to "let it out"! CHEEZ!! Hitting 80MPH the car shook uncontrollably!!
Put it in N and let is coast down, put it back in drive at 60 OK! Took it to 70 and still OK.
Finished drive back at 55 mph!
When buying that engine, person gave me a flat box with (2) flexplates. Getting back, first thing, was to check that flat box. THERE rested the CORRECT plate! Couple friends helped install and I handed them the WRONG ******* PLATE
Good or bad, never changed it until switching engine back to a 289. That same 5.0L is in
my 68 cvt WITH C-4 AND the correct plate