1972 factory c10 wheels tire size

[1969C10LSbuild]

Hello, I'm sure this has been asked many times before, so if you know of a link to answer please post it, I have a 1972 c10 at factory height and factory rear wheel wells, what is the widest tire I can fit on it without hitting the tub? Also include wheels size and backspacing if possible I want to maybe stick with like 15x10 torque thrusts on the rear and maybe 295s if possible also may do a 2/4 drop later on. Any help is greatly appreciated.