What is my max backspacing for these rims

[Dugan]

Im running a ford 9in with drums in the back of my 84 monte, I need to find what size rims I can run so I know what exactly to look for. Im running 26x10.5x15 mt slicks

What size backspacing range can I run for an 8in rim:
10in rim:

Thanks for the help in advance

I had to turn down 15x10 welds with a 3.5in backspacing for 50$ at a show yesterday because i was so uncertain whether or not they would fit. Im sure the frame side I would have been fine but on the fender side id stick out with those.

 

[pontiacgp]

what is the width of the 9" rear? You need to know that before you can figure out what backspacing you can run

 

[Dugan]

what is the width of the 9" rear? You need to know that before you can figure out what backspacing you can run

It is one of the professional custom built 9in rears i think i saw someone say they are 1.75in wider then a 7.5 rear Ill get out and measure it

 

[pontiacgp]

I have a 67 chevelle rear which is 2.5" wider then a 7.5 and I'm running 4.5" backspacing with 245-50-16 tires on 8" wheels and they just fit inside the rear quarters. I have the car lowered