on my 500 hp carb motors with msd boxes do i need to ground the purple wire with the plastic cap on it to set timing, did not do that a few years ago when i set it up and seemed to be fine.

TB-IV or TB-V?
No on the IV, yes on the V

2000 gen 6 how do i tell what tb it is.

I think in 2000 the 500EFI was being used but the 1998 and earlier HP500 came with either the IV or V depending on the year. The IV has a triangular module and the V actually has two modules piggy backed.