Those who have ordered custom back spacing wheels

[TwinsSpeedShop]

I just recently bought a step side, 67, very clean truck. I am in the process of ordering wheels for it and have the opportunity to order any back spacing that i need. Being that its a stepside, 20x10's are tight but doable I know. My hard numbers from WMS to bedside is 7". I want to order a 5.5 BS in order to get the most lip I can , but I don't need it to be outside the fender well either. What are others ordering for back spacing on step side truck with 20x10's. And yes I have searched and the numbers are all over the place from 6-5. Just trying to get some opinions and experience on what has worked and what is trouble.

The truck is a 67 with 71-72 wider rear, and will eventually be bagged. Not laying frame, but bagged.

Thanks In advance