Hey, Steve; welcome to the site. The Salsbury clutch from the 400 should fit the L297 and you may not have to change the springs and weights, although I'm sure the twin will rev a little higher. Trial & error may be the easiest way to check it out.
In answer to your CDI question, once the clutch is on and torqued, it generally stays put until you remove it. If you want to make double sure of it, you can use some valve lapping compound on the crank and inside taper of the clutch before you install it.
Good luck.
Stuck in the seventies- not in the swamp.
(6) Attex, a Hustler, a Super Swamp Fox, (2) Tricarts, (3) Tri-sports, a Sno-co trike, 3 Dunecycles, and a Starcraft! ...so far