Widest Tire/Wheel combo for a '72 Duster?

I will most likeley be going with 16" rims as there is a huge selection of High Perf. street tires availible for a very reasonable prices in this diameter. I'm not a big fan of big wheels, but it seems ZR rated tires in 15" are becoming more rare as time marches on.

I would like to go with 235 or 245 in the front and 255+ in the rear in a 50+ series tire (I don't like skinny rubber either, no 45 series tires for me, lol!). Is this possible without a spring relocation and or tubs/body mods? What backspacing/offset would I need in a 16 x 8 rim to make this possible?

Thanks in advance! :cheers: