I have no connection. I know there are a lot of truck guys ( and girls ) out in T land...
http://cgi.ebay.com/ebaymotors/model-t-truck-high-speed-ring-gear-worm-gear-5-1r atio_W0QQitemZ160387821829QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories? hash=item2557dbf105
That worm gear looks very pitted. It probably would tear up the driven gear in short order.
The president of our T club just purchased a Ruxstell TT rear end it has a 5:1 ring gear and worm, if interested call Mike Russell Columbia Mo 1-573-443-6759
Guys the correct phone number is 1-573-442-6759 Guess I couldn't read the phone book correctly