Advice asked for widthening rims on a 70 Duster

First of all: thnx so far everyone for thinking along and helping
I might have another solution with which I might keep my original 14" steel rims original. I have the opportunity tot get some steel 15" rims that come off a pt cruiser, it has 5 x 100 bolt pattern. Does anyone know if these will fit my drumbrake rear axle Duster? Especiially the backspace I would like to know. I can have the outer side widened for free to gain more dept. And how about the center bore. I think it might be slightly too small, but I could have that bored larger I guess. Opinions, marks or suggestions please? Thanx again