I put them in my PV, and within a week I'd ripped out one side of the rear floorboards (under the rear seat) where it attached. So I spent a while welding up some reinforcements and it's been rock solid for 5 - 6 years now. They typically send you a reinforcing plate to use at the mounting position, but my kit didn't have them, you'd probably want to use one for sure though.

After putting my sways on I too quickly came to the realization that skinny 185R15 tires were no longer going to be good enough. Prior to that the excessive understeer and excessive body roll really kept you from discovering how poor the tires really were. I soon replaced the stock wheels with some 15X6 Torq Thrust II's and some 205/55/15 sticky tires. Handles like a modern sports sedan now. (Bilsteins on it as well).
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'63 PV544 rat rod, '93 Classic 245 + turbo