69 Camaro mini tub backspacing?

[69Camaro]

Hey guys,

I will be ordering a set of Forgeline GA3's from Matt's Classic Bowtie's by the end of the month. I am building a 69 Camaro with Ridetech level 2 suspension, tru-turn and DSE minitub. I have not ordered a diff yet and I will measure that after I mock up the wheels and measure WMS to WMS.

My question is, what is the most common rear wheel back spacing? I will be running 18x11.5 rear wheels so I can use either 335 or 315's depending on tire availability. I would like to have a common backspacing so that if I want to sell the wheels down the road there is a better chance of them fitting other similarly built vehicles. Does that make sense?

Currently thinking of 18x9.5 front 5.75 BS, 18x11.5 rear ?? BS.
BFGoodrich Rival S, 275/35/18, 335/30/18

Thanks in advance for the help and advice, this website is a large portion of the incentive to build my car.