Monte ss frame notch tire/wheel question...

[AllMtR85SS]

im in the middle of frame notching my 85 ss. i have a 68-72 a-body 12 bolt. i notched to the factory seems top and bottom, and i have approx 13.5" from the inside of the frame to the outer edge of the lip. what is the biggest wheel size/ tire size i can run? can i make a 15x10 fit with a 305 or a 315? what backspace/offset? anything will help thanks..

 

[Wile E]

This might help. Old pic. 15x10 5.5 bs (rear). I notched to the seam, mini-tubbed and rolled the lips. Could fit a 295/50. A little more b.s would have made for a better fit. Not using the rims pictured.