Matt,

Your logic on how to test clearance appears sound.  I can't imagine that an extra 1/4 inch out from the car would cause a problem, especially with the 225s.  Of course, by 81, my car has the big fender openings for tires, but even on your '69, you are getting further from the suspension and I doubt that your tire was ever getting within 1/4 inch of your fender lip before the upgrade...

It would be a good test.  The logic is correct.  You could also just look at it without the spacers, and measure another 1/4 from the tire.

225/70s will fit fine with the 1/4 change.  255/60s may not.

I tried the spacers, doesn't look to be a problem. The only thing I could think of that I may get a few more knicks down the side from the wheels sticking out farther, but I was planning on clear mudflaps after the new paint anyway.

Thanks for helping me think things out. Ordering the new torque thrusts Monday.

Matt