Dr. Diff 8 3/4 axles

I need to get a set of BBP axles for my 8 3/4 rear. Do I want the 2" studs or the 3" studs? I am going to put drums on for now and may upgrade to discs in the future.

I'm not set on Dr. Diff so if there are any other Better and/or cheaper brands out there let me know.

Thanks!