I would just try this .... Visit your local Ford dealer's parts dept, with that driven gear in-hand, and then see what they stock in opposite pitch, and the right tooth count. I'm suggesting it because I spent many years as a Ford parts man, and that was a fairly common occurrence. That skips the whole "by application" process which can sometimes cause frustration for both customer, and counterman.
I had to change gears in my T-10 equipped '64 Gal as well ....and after determining which gear I needed, I just bought it locally (at a Ford dealer). This saves ya all that shipping money, waiting, and/or possibly needing to exchange/return it. Most Ford gears come as a pack of 2 or 3, to them ....so if say you bought the wrong one, I'm sure they'd exchange it out for ya .
Just an idea, and maybe a way to get you going again.
ps: Before you stab it back in there for the last time, try and brush some long lasting grease onto the drive gear, because it's steel and there's no oil bath back there on a T-10. The drive gear in my T-10 was solid rust and looked like it was dredged up from the ocean floor --just sayin'. Luckily I was able to come up with a new drive gear !
Hi Randy - yes, top left to bottom right.
Any idea who is likely to stock these things, and what do I ask for? Most companies don't appear to stock a different part for a T-10....