This is great to hear.
While 72blueNblue is right that the experiment had too many uncontrolled variables, I know what you mean when you expect an attribute to change and you observe something entirely different, it sets off alarms. I don't blame you for asking the question.
It sounds like you're on your way but I'll just add that I have these same torsion bars, Hotchkiss/Fox shocks and the combination seems pretty good so far. I think you'll like them.
Is your 1975 car really running the small-bolt-pattern? I've heard of some '73s (all /6 cars, IIRC) that came with SBP but nothing that late into production. Very strange.
Which wheels/tires are you looking at?