360 la weighted flex plate do I need to rebalance?

So, what you're saying is that your engine IS still externally balanced; and NOT internally (i.e. neutral) balanced, correct?
Then you should be fine with the B&M 10239 flexplate (if using a 904) or 10236 (if using a 727).
BTW, I would confirm with PATC (with pictures) that you actually do have a neutral balance convertor, and either get the correct one that you ordered or be compensated for your trouble; and not just give him a pass with "Well, I wouldn't ever forget something like that". That's BS. Would make me wonder what else didn't get done "quite right"...