Standard Motor Products (SMP) part numbers
4 inch International Harvester (IHC) Cap with Male Terminals: SMP# AL-482
Rotor for Ford Distributor & 4 inch cap: SMP# FD-115
Heavy duty 351M/400 8.5mm ignition wire set: SMP# 69404
The wire set includes female coil to male distributor cap wires in 2 different lengths, and one long male coil to male distributor cap wire.
I think this is what you're looking for. The wires are long enough for the 351M & 400, which is a little longer than 351C wires. I don't understand how you plan to route them, so I don't know if they are long enough for your intentions.
There shall be no problem with cross-firing caused by the smaller diameter cap as long as the engine is in a good state of tune, and the plugs and ignition wires are in good condition. The ignition shall only “cross-fire” when doing so provides a path to ground that is easier to travel than following the proper path to ground would be.
These ignitions were designed to ignite some very lean air/fuel mixtures diluted with exhaust gas (EGR); thus both Ford and GM engineers encountered cross-firing with the 4-inch cap. However, if your engine is equipped with a carburetor or fuel injection system providing a better air/fuel mixture the likelihood for cross-firing is reduced. I hope that makes sense.
-G
