Engine Coolant pipe

I used a rubber cap to plug the port off that went to the heater pipe and left the other hose to the thermostat housing connected.

I don’t have any info on the cap. I just got it at the auto parts store.

That’s not entirely true. You could go with a clockwise water pump, but you could use the counter clockwise pump you have now too. If going to a cw pump you use a crown Victoria pump, but I believe you need to switch the backing plate to your mustang one because the timing covers are different. If using your ccw pump you just need an alternator relocation bracket. Jegs, on3, breeze, and others make them.