Not to sound like a jerk, but are you sure that you have small bolt pattern wheels? After 1972, Abodies all came with LBP wheels and disc brakes up front.
There were some models in 1973 that used some leftover drum assemblies for the font wheels, but I've never heard of a 1974 having front drums.
With a stock A-body 8-1/4" rear, 3.5" or 4" of backspacing will suit you well. You might be able to pull off 4.5" backspacing, but that will put the tire very close to the spring perches. It depends what kind of tire you run.
You can go a bit wider on a duster than you can on a dart, but I think a 255/60R/15 will fit well on the rear. With this tire, I would not run more than 4" of backspacing on the wheel. I believe most stock 15" x 7" steelies have ~4" of backspacing, but you will need to check with somebody else to confirm that.
For the front, you can still run a 15x7 but you will be better off running a 225/60R15 or 225/70R15. This will provide better clearance up front with the steering at full-lock while still giving you decent traction.
Also, welcome to FABO!
-Mike
