Did you try moving them so they were straight up and down and then run it some more with similar weather and DA at the same track? If not, maybe you should

Remove the cobwebs leaves .... run it. Unless you want to work on it.

built and used leak link stuff back in the day, for what you are doing should work fine. Never used on a car faster than 10.50 make sure the housing floaters are free and not binding and the front spring segments should be clamped, the front spring segments are acting like a 4-link bar so any flex should be removed. The other con is that it is a heavy system, but again just for street and occasional track use, and you don't need every tenth out of it or try and put 1000HP to the rear tires it will work fine. I would also maybe try a better adjustable type shock.

I wouldn't street drive a ladderbar set-up...seen a few break.

I agree. Full out race car ladder bar are fine, but for a street/strip car I'd go caltras or super stock springs.

A friend has ladder bars on his 41 Ford, for 35 years, 4 speed too

The obvious question is "Where did they break?"

Anything with poor welds will eventually break.
Poorly designed brackets will break.

I haven't decided yet whether it will stay or just go with leaf springs that are moved in (which these are).

The ladderbar itself, and then the rod ends. the driveways and potholes and turns etc are hard on a rigid suspension. With that set-up you have I'd do a Caltrac personally, and put the typical shock on it for that application.

Interesting thread title. I recently came across some pics on Facebook, in the 64-71 race Hemi group. A restored 67 GTX that actually had a leaf-link rear suspension. It was a nice car. No recollection of whose or where, though.