Found two of these for fl350. Trying to figure out which can arms to use and spring. Anyone use one of these? It's going in my buggy with leckich Engine.

that's the big bore leckich right?

I'd start with the purple spring part number 207888A. You can also buy shims so you don't have to keep buying replacement springs. Just watch for blocking. Spring mainly affects engagement RPM, but also will slightly increase peak RPM as well.

Then depending on your peak RPM needs the cam arms should be about 43g, that can be had with I believe the old style 'C' arms, or the newer style 'C-2' arms part number 208964A. Different arms have differing profiles and weights which you can dial-in to obtain and keep your target RPM. I'm not so great with the 102c in this regard but you can start with arms around there.

What are you doing about the driven? I'd recommend either stock salsbury or Comet 790 with the RED spring. If you have any more white springs you can try it but the RED spring I've tried and is better IMO.

My guess is this would give you an engagement of about 5000rpm and a peak of about 8500.