Your auto died because you put a ton more power through it and didn't do anything to help keep it cool or better lubricated. With a J-mod and a good dual fan B&M cooler that trans would likely still be alive and kicking.
The 3650 is fine. Just because you know someone who had a bad experience doesn't mean they are all garbage.
Also if your goal is to go fast in a straight line, keep it auto and swap in a fresh trans and an aftermarket stall converter. You'll run better 1/4 times with that setup than you will with a stick all other things being equal.
2000 Mustang GT Steeda build #48. Bolt ons, suspension, Novi 2000.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.