205 70 15 front = 26.3 diameter
255 60 15 rear = 27.1 diameter
front offset needs to be at least 4 inch
rear offset needs to be 4 1/4 to 4 1/2
( better if front rim 15x6)
I know 15x10's reversed crager ss wheels will work on your charger with no problem as long as you have air shocks installed in the back, my son has them on his 68 charger with a 295-50-15" tire.
the deep dish crager 10" rim works great on the charger, son has them on his 68 and has a 295-50-15" tire on them, I think the backspacing is 4 or 4.5".
reach up under the dash and unbolt them.
there are 4 nuts under the car...
chiltons repair manual from the library will have the answer.
on the right front corner of the transaxle
Because the wheel will rub / hit the front brake cailbers and rear drums. The 91 was built for 16 inch wheels, are bigger
under the altnator (bottom front of the passenger side).
Under the passenger side of the car just in front of the rear wheel.
try manciniracing.com and see if they offer it.
It's on the back side of the oil pan.
Take it to an alignment specialist and have it done, you can't do this at home and get it set right.