wheels size help for dropped 69 step side

[anviltester]

So I've searched and searched finding nothing that really helps. I only want to buy 1 set of wheels and tires and do it right the first time. I've got a 69 step side with porter built mild rear drop setup and stock front member w/ 2" cpp drop spindles and porter's body drop. i know 20+" wheels are out so I'm looking at 18's or 19"s. running 13" wilwoods w/ 6 pistons up front and 12" wilwoods w/ 4 pistons in the rear. i have some old 15" wheels and tires at 29" tall but they are a bit too wide and hit the fender lip and the upper support bar. Does anyone have a proper tire size that will stay under or at 29" tall and still fit in the side the fender on a 18 or 19 wheel? also what backspacing to use for a 5 on 5 bolt pattern? many thanks to those who can help.