What rear drums for 4.5" axle swap

Thank you for the explanation, kinda figured it had to be the flange itself. I am so used to 8.8 Mustang stuff.

Appreciate the in depth explanation.

Going with 10", it is what he has off cars right now so easy decision. Plus new stuff seems to be alot cheaper for 10" system, I have no idea what condition the stuff is in, priced out replacing all of it and its pretty cheap relatively speaking