sorry..."sliders"?...was wondering if I should run "slapper" bars or solid mount ladder bars.
Not sure how "sliders" would help either Bob; at least what I'm thinking as sliders.
Sliders do the same thing as spring shackles, and if mounted on the end of a spring they allow the spring to "grow" as the rearend moves. If mounted to the end of a ridgid ladder bar they would need to be vertical to allow the bar to move vertically as the rearend moved vertically, but that would still stop the rearend from moving back as it compresses, so still bind.
If you mount ladder bars solid, then you should use floater mounts on the axle, so the rearend can move freely in an arc and not bind when using ladder bars with leaf springs. The other option is ladder bars with coil over shocks, and delete the leaf springs. This is usually a major suspension mod, and a panhard bar is also needed.
This is a Comp Eng. floating axle mount:
Anothe Comp weld on mount. This weld on has the added feature of being able to select three height adjustments:
I saw an early 50's Chevy gasser that runs around here locally that used a unique mounting method to work out the binding issues with his ladder bars and leaf springs. He used a small Speedway shackle to mount the front of the ladder bars, and mounted it pointed back at 45 degrees. This allowed the ladder bar to move up and back as the spring compressed and moved the axle rearward. He said it worked well with no spring binding. I would guess it still did OK controlling traction too.