England air internals work really well, though for damping you have to change valves as no oil. Still great but oh so rare.
Risse and white bros as mentioned mates with springs
I was once going to swap in some damping carts from a Judy DH, so you get rebound and compression but they got lost in customs which was gutting as we're NOS. Red qno and silver alloy bodies iirc.
I've heard you can retro fit the hydracoil internals from newer forks, and you can plonk a sid CSU and internals in the lowers. You might be able to do the same with pilot as well?