If my memory is correct the original sway bar on my 69 Z28 was 5/8 and I am not finding any that size listed anywhere. I replaced it with a 3/4 bar (across the counter part) .
I would like to find a 5/8 bar and a 3/4 or 13/16 bar.
It seems that a little known fact is the rear bar from Chevrolet was virtually identical to the front bar, the only difference being the angle of the eye was just a little bit different, but not enough different to keep the front from being used on the rear
Thanks

 

5/8 is correct for the rear bar, the torsional stiffness of a 3/4" is 120% greater (overkill).

 

The plan was to put the 5/8 bar on the rear and put a 3/4 on the front. Back in the day just took the front bar and put it on the rear. What was sort of funny was GM priced the rear bar a lot higher than the front and they were virtually identical except for the different angle on the eye. maybe 10-15 degrees more bend

Now if could just find a tire as big as what used to be available , so far nothing even close for an 8 inch rim . Back in the day had about 11 inches of rubber on the ground in front and about 12 in the rear, and yes they were designed for an 8 inch rim. Trans Am rim width rule and yes they looked sort of funny and were hard to put on and take off. but they worked great. The Firestone tire was even worse than the Goodyear as it literally had square sides and was hard to get a bead breaker on it if you can imagine a square donut
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Building an autocross car for the daughter and building it sort of as a vintage car like I ran back in the day. It surprised a lot of "sports cars" like Corvettes and Porches back then. The 67 about 4-500 pounds lighter than the 69.