Mac Toe, H-Body "Stop Hop's" aren't made any more if I recall correctly, there was someone on here that offered the plans to make your own, but that will take some searching for. Now this is only my take on them,
"BAD IDEA"! Those parts would work by preloading the rear end housing against the weak lower control are mounts, on the chassis. Now what that is trying to fix is poor geometry and components that weren't built for the power you are applying to them. Most everybody that get serious about making even a little bit of power in these [low 200's HP] add an elevated upper control arm mount to the rear end housing, that apparently helps a lot. next up seems to be the control arms themselves, a couple of ways to fix those up, Buy new ones tubular [UMI, AJE(?) and others (like Overkill Racecars, but he hasn't had time lately to deal with these "product pieces", as that is a smaller part of his Chassis shop business and long time h-body.org guy) not many suppliers left to choose from
] You maybe able to make your own, or the cheapest easiest fix would be to "Box" the factory ones yourself, I would think something as thin as 16 gauge steel would do the job. [That material will be in tension as the "C Channel" arms (14 Gauge/2mm+/- {?}) are trying to flatten out under the "pull" that the upper are in while launching the lowers would likely want to collapse under Compression, but also may try and flatten out so weld in the sway bar spacers (or add your own) and box them up this will let you improve the geometry and fix the weak parts that exacerbate the situation. I hope this gives you a good "Jumping off point" others will weigh in. Harry
I'm not a hoarder I'm a preservationist 78 Monza Spyder (~Soon(ish +/- I guess) To Be 2+2 with Spoilers)