#12 wire is available in any length and color you want at most every auto parts store. There's no need to pay outrageous prices for a dedicated wire. If you want the locking plug that attaches to the distributor cap terminal, just scavenge one at a salvage yard and do a Western Union splice covered by a piece of heat shrink tubing to the wire you attached to the ignition switch. If you want to use the original terminal block connector on the firewall to make things look somewhat original, just pick one of the connector slots without a wire in it, drill a hole through it, and thread the #12 wire straight through.
Jerry
