I have done this on a 1970 Mark III about 5 to 8 years ago.
The factory front sway bar is hollow. And not that effect, IMO
I replaced the original front bar with a solid 1" or 1.25" bar from ADDCO. I forget the exact diameter.
The change/improvement is significant!
In addition to that, I acquired a 1973 Mark IV and took the factory rear bar off. (There is no rear bar on a Mark III from the factory)
I have that rear bar in Phoenix. Unfortunately for me, the Mark III is in Michigan. So, the rear bar is not yet installed.
Know that later Mark IVs have a larger rear diameter bar. 74 to 76 I think.
Good luck
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