This is partially the reason for the post. I was under the impression the HD bars and springs were based on the Formula S package.
My 68 is a /6 AC car which I read here also got the HD suspension … that got me wondering about springs as I believe T-bars are engine based.
It ‘appears’ /6 A/C got HD all the way around even with the 7 1/4 readend.
Without A/C the T-Bars are significantly smaller (drag race bars).
Learn something new everyday.
PMW