cannot stress enough that the number one fuck up moped people make when building race bikes is spending thousands on their engine and putting on some cheap ass moped tires and not dialing in their suspension- races are won by carrying corner speed. Do whatever will help you brake later and get on the throttle earlier.
so on that note some thoughts:
1. Both adjustable compression and rebound damping are important. Especially when you're building an entirely new suspension linkage. You'll want to be able to manually adjust as well as spring tension for your weight.
2. spend time playing fork spring springs and oils to tweak those characteristics in the front. Moped folks seem to set their forks up to be waaay stiffer than optimal because I think the perception is that's better.
3. Get the widest and softest tires that you can fit and run them with way less tire pressure than you would on the street. My crf100 minigp bike with bt45s I run 17psi in.
4. read up on cornering theory and race craft, Keith Code's "Twist of the Wrist" is a must-read, and get lots and lots of seat time.