I don't know whether to post here or in Tech Tips, but here goes.
I restore vintage Mustang harnesses on the side. Recently, I was asked to fix up a 1969 tach/AC harness for a Mustang. Since I had never seen a Cougar harness, and I had read where other people had used them, I said "sure...why not? I can learn things!" Well, it came in, and was in very good shape. But there were some "dongles" and wiring extras that after tracing the wires, found that I could simply ignore them. However, the connectors to the tailight harness were so radically different, that one couldn't plug in a Mustang tailight harness. I had to replace those connectors. The dash cluster connectors were not in the same location of that of the Mustang, so I had to re-pin them. The e-flasher power did not come from the fuse box, but from a 15 amp circuit breaker tied directly off of battery power (unfused). I had to install a fuse clip and proper wiring for it. The changes were probably more involved than converting a Mustang non-tach harness to tach.
I feel really sorry for folks who do attempt to use Cougar harnesses, as they will probably run into trouble putting them into a Mustang. You'll have to use the entire Cougar wiring assembly and dash to make it work. AFAIK, Cougar wiring is not available as repro's, so one is much better off going with Mustang wiring.
I restore vintage Mustang harnesses on the side. Recently, I was asked to fix up a 1969 tach/AC harness for a Mustang. Since I had never seen a Cougar harness, and I had read where other people had used them, I said "sure...why not? I can learn things!" Well, it came in, and was in very good shape. But there were some "dongles" and wiring extras that after tracing the wires, found that I could simply ignore them. However, the connectors to the tailight harness were so radically different, that one couldn't plug in a Mustang tailight harness. I had to replace those connectors. The dash cluster connectors were not in the same location of that of the Mustang, so I had to re-pin them. The e-flasher power did not come from the fuse box, but from a 15 amp circuit breaker tied directly off of battery power (unfused). I had to install a fuse clip and proper wiring for it. The changes were probably more involved than converting a Mustang non-tach harness to tach.
I feel really sorry for folks who do attempt to use Cougar harnesses, as they will probably run into trouble putting them into a Mustang. You'll have to use the entire Cougar wiring assembly and dash to make it work. AFAIK, Cougar wiring is not available as repro's, so one is much better off going with Mustang wiring.