Wheel Width and Off Set Need Help

[bubblerboy64]

In the process of replacing wheels and tires I need some one to check
the width and off set to see if I am heading in the right direction.
The back axle has 20 inch tubed tires on it and my goal is to get six
tires and wheels all the same so that a spare would have a chance to
work. I need all new tires so I have decided to get rid of the ole
20 inchers in the back and replace all 6 wheels as well. I know I
need 10 bolt stud piloted wheels and we were able to get the hub hole
dimension and the stud pattern dimension the questions unanswered are
the wheel width and the off set. The fellow THINKS its a 8.25 wide
application and a 6.62 off set. I told him I would post and see if
this is correct to the best of every-ones knowledge. We can return
the wheels if not right but it would be nice to get it right the
first time. Now the information needed is that my axles I believe
are off of a 1978 FC so any of you fellows who have late seventy BB
FC's would you check if you have records as to wheel width and off
set? If 8.25 and 6.62 is not right I need to know as soon as
possible. Thanks again. Going with Michelin XZE tires.

John Heckman
central Pa
1973 FC