There are lots of people on here that will give you excellent advice as to when to get billet drums or which valve body to use but I suggest you research who is best at mopar transmissions.

Often you get guys who have only built GM trannies selling themselves as building anything.

I can tell you from experience there are nuances for every transmission and some shops may not understand what really is good or bad for a particular brand build.

Get references or ship it to one of the guys on here that build them and know them.

Hope it is some help.