Need some help with wheels! Having issues

[bmasso]

I have an almost complete 1974 Duster that I'm having difficulties finding accurate information about wheel sizes. The car has altered suspension and does sit about 1.5 inches lower than factory although the exterior dimensions from hub to hub are the same as factory. I did purchase some 20" wheels for the car and have a set of wide rears that fit perfectly while the fronts are a positive 35 offset and 8.5 inches wide with 255/35/20's that are not clearing the corners of the fenders. The wheel looks great but clearly will not work. Anyone fit some big boys under the car that might be able to give me their dimensions that work. Want as large a wheel and tire as possible, but may have to do a staggered 18" front and 20" rear(not what I was hoping for). Any help would be appreciated