Need wider rear tire for 77 camaro

[Street Fighter]

What is the widest rear tire I can put on the rear of my 77 Camaro without tubing it.I have p275-60-15 on 8" wide olds rally wheels on the rear. can I get a set of 10" wheels with less back spacing, which would place the tire closer to the outer fender which may allow me to go wider on the rear tires. I am runing BF Goodrich tires which I have found to be a little wider than a lot of tires. I am not ruling out tubing but there is no one here that does it.

[cammed goat]

I am picturing your car with a set of the OEM rally wheels GM used for the Corvette, Camaro, and Chevelle SS but in a staggered form. Try looking those up because I am tempted to say they are available in 10" width. I could be wrong. Check out Wheel Vintiques. They have 10" rally wheels.