Paul,
I used an eighteen circuit Painless loom (harness in 'merican) and it was first rate. The handbook is actually worth having as well. Even though it is made for your typical hot rod, they give you enough extra length in the circuits that I had enough in nearlly ever case.
Since I went EFI, I appreciated having the extra circuits, but if your electrical system is fairly simple, they do make setups with fewer circuits and lower price tags.
Regards,
Lynn