If you're building a racebike from scratch, PGMII is definately the way to go, I can't believe anyone would choose anything else unless they actually want (or need for class reg rules) a pure mc16/mk1 mc18/mc21 or mc28.
The other options are all a lot more expensive, more complex and possibly not as good when you bear in mind both F3 and RS PGMII's will just plug in and work.

The only bad bit is there is no such thing as an mc18 race loom except the F3 stuff which needs the F3 stator, pickups and HRC clocks.
But making one from an r5k loom isn't tough, don't forget to do the wiresplice.

The only real alternative might be an Avgas PGMIII, but they're even harder to come by and more expensive than HRC carded PGMIV's.
And mc21 race looms seem to cost a lot on Yahoo Japan.
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