I don’t auto cross at all, but I have seen how it’s done.
Knowing what kind of regulations there are for clutches will determine to point you in the right direction
If there are no regulations, then disregard my comment, and find the most durable and tough clutch you can get
I personally do like the Steell Nytro 3 or 4 disc clutch, if I recall it correctly they were purple/burgundysh in color, with the black drum?
I absolutely loved them, as they were very durable and tough, but the class we currently run with uses a different spec clutch.
I think you should continue to use that old Horstman Steel Nytro clutch till it breaks, and then buy a brand new one with a 4 disk, and adjust your stall speed to your best liking. That’s just my opinion. Hope that helps.