Speedometer driven gear issue

[msinc]

I have a "big input" close ratio toploader in my Superformance with a Robert Pond aluminum 427. I got this car in December and the speedometer was off. It reads about 10mph slow. I got on the web and found the formula to figure out which gears I need and was able to determine that I needed a 16 tooth driven gear. The car had a 21 tooth installed when I got it. Seemed like a legit finding so I ordered the gear.
I saw where the toploader had a different set of gears for the Galaxies. Seems they have a cable assembly that enters the tail housing on the drivers side and require gears that are slanted opposite of the ones that go in the passenger or right side.
My trans has the cable entering on the right or passenger side so I ordered the driven gear accordingly. Mine has a 6 tooth beige colored {probably discolored white} on the output shaft. Upon initial inspection it appeared to be fine and by the chart I saw also appeared to be the correct gear.
I got my new gear, installed it and it did seem to be reading the speed correctly. However, about 1/2 mile worth of driving and the speedometer ceased to read. I pulled the gear and you can see in the photo below that it is wiped out. It also appears to be slanted differently than the 21 tooth red gear I had. The red gear did operate the speedometer, just not accurately.
Not sure now if the new gear is incorrect. My problem is that every photo I see of a driven gear for a right side cabled toploader slants just like the white gear that failed. Doesn't seem right to me that you could have the left side cabled gear in a right side transmission and just install the other gear and have it work.....someone out there has to know what I have here....any help or info is greatly appreciated and as always, thanks in advance !!!!!!

Edit: sorry, I forgot to attach the photo