Wheel width

I am now the lucky owner of a set of 15x8 Draglites for the rear of my Dart, to replace the steel 15x6.5s that I have.

I still need to buy a set of front wheels. Will I be able to run 15x7s on the front? Or will they rub when turning?

Also, I am concerned that it will put me back to the same problem I have now. My front track, with 15x6s is visibly wider than the back (with 15x6.5s). If I have 7s on the front and 8s on the back, will it result in the same appearance? Am I better to stick with 6" rims on the front?

Also, what backspacing shoudl I run? My only choice with the 6" Draglites is 3.5" backspace. I'm not sure what weld offers in the 7" range.