Tire size help

Can anyone tell me what's the widest rim you can fit on a 69 charger not tubbed I have cal tracs on it in the stock leaf spring section. I'm looking at getting the right drag racing rims for next season. I'm using a 8 inch rim with 28/10.5/15 M/T slick. I was wondering if a weld 15x10 rim would work and what back spacing would I need or do I gotta go with a 9inch. Any help would be appreciated. Thanks

Anyone know?

I can't help with the max wheel size, but you might consider a 9" slick. Had my best times and hook on the belvedere with a Hoosier 9 x 28 on 8" wheel. Had to readjust the clutch pressure & relearn to drive because it was dead hooking. Just a thought