We’ve had very good luck with the Stinger shoe/drum clutches on clones.. They hook up well, are relatively cheap compared to disc clutches, easy to work on, etc. Our club mandates them for junior clones and also for our Senior “sportsman” class. They seem to run forever – I’m paranoid, so I tear ours down and clean them monthly during race season and rarely have much buildup/glazing on them.
I’ve also heard good things about the Mongrel, although those were on lower HP and weight junior karts, so I can’t say how they would work on a senior setup.