I have a 1988 Bounder with the P32 Chassis. I had the same problem. If you consistently burn the same wire it is an indicator that you have an exhaust leak that is directing hot exhaust gases right at the sparkplug wire.
Most cases, you can't reroute the wire because the hot spot is really close to the plug.
I fixed mine temporarily by figuring out where the leak was and making a shield that kept the hot gases off of the wire. Note, the shield will work best if it is not touching the wire, just make sure that it is between the hot spot and the wire.
My permanent solution was to add Doug Thorley headers. No more burnt wires.
'88 Bounder on a P30, Gear Vendors, Thorley and other goodies.