Front Suspension Confusion

The '73 disk set up does stick out significantly further, the difference is close to a 1/2".

And a 12mm difference between a -6 and a +6 offset is also significant, that's also almost a 1/2" per side.

I ran 225/60/15's on my duster with 15x7" police rims, which have a +6 offset (4.25" backspace). The car was lowered from the stock height and had no issues with rubbing, although that's about as wide a tire as you can go with that backspacing.

As you know, the ride height also changes the alignment pretty substantially. Being raised up that far can make it impossible to get the correct alignment.

Also, is your alignment guy using the stock alignment specs? Because if you're running radial tires, the stock specs are wrong. Stock alignment specs are for bias ply's, which require alignment numbers almost opposite from radials. You should be looking for -.25* to -.5* camber, as much positive caster as you can get (usually +3* or so with the stock suspension parts), and about 1/16" toe in.

The car still looks like it's ride height is too high to me, but stock was pretty high and none of my cars are at the stock ride height so that may be part of the problem. And those 185's look like a pretty short tire.