63bel

hi my name is greg and im new to the forum,im building a 63 bel air 4 door into a mild street rod for my family and i to cruise in and go to car shows etc, i am building a 383stroker motor for it and was wondering if anyone out there can tell me what the stock rearend size is and if it will hold up to roughly 500 hp. i do know that the rear is a "front loader"with 3.08 gear. i wanna buy a locker for it but dont know what size to get. is the ring gear an 8.5? i cant measure it without pulling the whole pumpkin apart,and dont wanna do that until i know what size posi locker to get. anyone help me