I'm sure the 73 is the same as the 71, I'll check at work tomorrow, but my 71 conv does not have a fuse for the top. It should have a circuit breaker located right near the starter relay. The power window feed from the same c/b but it feeds a relay which is powered by the accessory stud on the fuse block. It sounds like the c/b is bad, you can test it to see if it has power on both studs, if not use a jumper wire and test the top real quick.
Also be sure the power lead to the relay is hooked up to the same post as the battery cable on the solenoid.. I had a COugar onec tht had power windows that didn't work. The problem was the wire hooked to the starter side of the solenoid.