what size backspacing do i need for an '89 notchback with a 9" rearend narrowed 1" on each side to fit 325/50r15? it's also mini tubbed.

 

Sounds like you will have to do some measuring, because I don't know
what width wheel you want to run and also don't know the measurements
of these mini-tubs.



For starters, measure the distance from the mounting face of the hub
(drum or rotor - whichever you have) to the inside of the tubs.
Are any brake lines or control arms in the way?