How wide of a rear are you wanting to run? I have a '68 RR and I'm currently running a 305/40/18 on a 10" width rim with absolutely no problem.

I would think you'd only want to mini-tub if you're planning on running a 12" width rim which was a little too wide for my tastes.

FYI........I'm located in Houston if you want to have a look at mine.