1970 DUSTER WITH DISC BRAKE CONVERSION WHEEL HELP

Myself I would use a 15 x 6.5 factory ralley on the front. The 15 x 7 is to wide and the 15 x 6 , there is no trim ring for the 15 x 6
that matches a ring for the rear wheels.
If you buy any aftermarket wheel , measure the backspace on each wheel , to make sure they are the same , correct. I have found a number of wheels that were just plain wrong.
Also on the rear , a lot of times the rear end backspace is not the same on both sides So try a wheel on both sides to see what fits best.

Frank