MAX Tire size withot narrowing the rearend

My question is without narrowing the rear end and just having a mini tub, what is the biggest tire size I can have on my 1970 nova?

I also want to know if Competition Engineering's leaf spring relocation Kit, moves the leaf spring 2-3 inches inward to fit bigger tires needed.

I want to have a least 11 inch tires without having to narrow the rear end, Is this possible with a stock 12 bolt rear? and if the wheels Can fit what backspacing would be needed to fit 11 inch tire on a stock rear end.

Thanks for helping me out.
Art :devil::bored::horse::prost::ragtop::smle/mad::skull::skull::skull::skull::skull::skull::thu mbsup::notworthy::BDay::bounce::salute::jumping::s mle/mad:

255's will fit pretty easily. Some people get 275's in there.

275's easy.
28x12.5 with an 8inch wheel and 5.5 inches backspace....no problem.
Shocks must be moved inboard.

i think hes talking about with a minitub? am i wrong? if thats the case you could easily fit an eleven inch tire in there