17" Wheel backspace suggestions please

[Dual quad]

I'm thinking about some AR Torque Thrust II's for my newly 4/6 ECE droppped '72 SWB, but I need some suugestions on backspacing. I don't want to spend alot of cash and end up having to use spacers or have the wheels too sunken in the wheel housing. Here's what I'm looking at so far.

Front - 17X8 wheel (4" or 5" BS standard), 255/50-17 tire (27.0" tall)

Rear - 17X8 wheel (4" or 5" BS standard), 275/50-17 tire (27.8" tall)

AR also offers a 17X9.5 wheel with a standard BS of 5" that I could use on the rear, but I'm not sure how this would fit.

It may be that the standard backspacing doesn't work for our trucks and you need to custom order . Any suggestions on backspace are appreciated.