TR-3650
Does anyone know anything about this transmission?
Is one made to fit a third gen?

http://www.ttcautomotive.com/products/tremec.asp

 

This is from a Ford product web page...after reading it looks like not worth the effort being weaker than the T-56 which is a known swap for our third gens. Hope this helps.

Tremec T-56!
The added power of the 2003 SVT Cobra meant that it was necessary to find a beefier gear box. The Tremec T-56 transmission was the perfect fit. Not only is this transmission significantly stronger than the Tremec TR-3650 that it replaces, but it also has a sixth gear that enthusiasts have been wanting for quite some time. The ratios are also different through the first three gears from that of the Tremec TR-3650. The T-56 used in the 2003 SVT Cobra does not appear to be a carryover from the 2000 SVT Cobra R as the ratios have been somewhat revised. The 2000 SVT Cobra R had the following ratios:

1st Gear - 2.97
2nd Gear - 2.07
3rd Gear - 1.43
4th Gear - 1.00
5th Gear - 0.80
6th Gear - 0.62
Reverse - 3.28