ARE you saying stay with the factory rally's that i have now ? WHAT is the b s on factory rim? on the box its says 6mm off set is that the 3 1/2 inch back space.
+6 offset is 4.25" of backspace on a 15x7" rim, which is what most of the OE mopar 15x7" rims from the late 60's up had. Most of the aftermarket 15x7" rims are 0 offset, which is 4" of backspace.
3.5" of backspace on a 15x7 works out to be -13mm of offset. Not good.
With a 15x7 in the front you want at least 4.25" of backspace to maximize tire width. Ideally you would want more like 4.5" on a 15x7 in the front, so you can run a wider tire. There's plenty of room to the frame. But 15" rims max out at around 4.5" of backspace in the front. You can go a little more, but after that you start hitting the UCA/brakes. If you go up in diameter, like to 17", you clear the brakes and UCA's and can get up to 5.6" of backspace before you hit the tie rods. With 18's frame clearance is the limiting factor, as the tie rod fits inside the rim. Which is why the guys with big fat pro-touring tires use 18" rims, at least on A-bodies. :D