17 inch Mustang rims..

I just discovered that when I went from front drum to disc on the '75 Duster that I had to move from SBP to LBP.

I had planned on moving to 15s in the back so I have a set of (aluminum ?) adapters to go to the LBP

I was reading the post of Snuffys Duster and he put 17 inch Magnum/300 rims on his car...I was kinda freaking out about the cost of new rims/tires until I remembered that I had a set of aluminum rims / tires off of a '07 Mustang GT. So I tried the fit and the adapter fits perfectly.

I did a search on this site and someone was putting a set of bullets on his car but the rear tires rubbed the springs so spacers were required. If I use adapters, that wll solve this problem. Correct ?

I also tried to find the offset on my mustang rims and I think it is 40mm offset.

Will these fit my car without mods to the fenders?

I am not in love with these rims but it will be a good stop gap measure until I can afford new ones.

Thanks
ian.