Well, I guess I had better do a follow up to this thread and post what is happening at this time. Got the new gears and a gasket for the tail housing. Pulled everything down and did a few tests before I just change gears again and put it back together. First, I reinstalled the speedometer and got a brand new cable. I pulled the cable wire out and lubed it as well as the cable jacket with GL-4. This was done at the advice of John {ERA174}, who has been very helpful.
I installed the new gears and before I put in the cable with the gear on it I measured the torque, in inch pounds, required to keep the output shaft in motion while the gear box was in neutral. Then I installed the cable and driven gear assembly and measured it again. No discernible difference. Then I sprayed each gear with flat black spray paint and did a roll contact pattern test, similar to checking a new ring and pinion. I was looking for any possible issues with the way the gears meshed. That all looked fine. Unable to find anything that looked like it might be a possible problem, I did the final assembly. This time I soaked each gear with gear
oil and took the car for a test drive.
I am happy to report that after a 12 mile test drive the speedometer was still working and read the correct speed. I pulled the driven gear out at this point and inspected it for any issues. None!!! It looked as good as when it was installed. I have since driven the car another 36 miles and the speedometer is working just fine. I believe the problem is solved.
I want to report a few things too...I did in fact search and read every possible thread regarding speedometer gears, looking for any info that might be of some help. What I found was what I believe to be some bad information. Several posts referred to "different" or "top loader specific" gears that were a must to solve this problem. It was repeated several times that "you couldn't just order Ford speedometer gears, you have to get the ones for a top loader"....this proved to be not sound advice and simply not true. Everyone {pretty much} is aware that there were left side entry and right side entry gears with the teeth cut differently, but there are not any other magical mystical "top loader specific" gears in existence.
I hope someone finds this thread useful and I am very gratefull for all the tips, info and help I received!!!!!