Richard:
I recently put a set of wires on a motor that were supplied with a heat shield, I think it was an extra cost, and the wires werent cheap but the quality was top notch. They installed from the top, but so far no problems with header heat. The boots and wires are silicone, and the heat shields were a woven heat resistant material that went over the boots.
Check out Nology wires
Cheers
Phil