Recently I have seens lots of post regarding the manual swap so heres a summary of what you should know abouth it and what is the best transmission for this kind of swap.
Information is provided by Tremec and rating are for stock transmission. http://www.ttcautomotive.com/English/products/tremec.asp T-5
-Can be found in any older fox body mustangs
-will only fit the 92.5- car because of it,s bolt pattern that is common to the 5.0 and 5.8 engines.
-Rating 230 lbtq on a 5500 lbs GVW
-Should not be used in stock trim as reliability will be and issueT-45
-Can be found in the 96 to 2000 mustangs
-Will fit any 92.5+ car.
-Better torque rating at 325lbtq on a 3260lbs GVW
-Non performance/racing driving style recomended due to lower hp and tq ratings but it should be upgraded to higher torque capacity to be reliable.TR-3650
-Can be found in the 2001 to 2010 mustangs (05 to 10 uses hydraulic clutch set-up)
-Will fit any 92.5 cars
-Rating 360lbtq 3260GWV
-Better torque rating over the t-45 for stock and mildly modified carsTKO 500/600
-Unit never came stock in any mustangs
-will fit ANY cars with proper bell housing
-Excelent torque rating at 500 lbtq or 600lbtq depending the model
-high performance transmission that is rather rought and noisy.T-56
-Can be found in 2003/2004 Mustang cobra and the 2000 mustang cobra R
-Will fit any 92.5+ cars
-Excelent torque rating 450lbtq
-High performance transmission with 6 speedsT-6060
-Can be found in the 2007 to present Mustang shelby GT500
-Will fit any 92.5+ cars with modification on the trans crossmember and drive shaft and hydraulic clutch conversion.
-Excelent torque rating at 600lbtq
-High performance transmission with 6 speed
Keep in mind that the spec are for bone stock transmission regardless what the aftermarket has to offer.
Many transmission specialist will be able to up-grade any of theses transmission to fit higher torque rating.
Most of the basic up-grade are:
-1/2 Gorilla Shift Fork
- Cryo Hardened 10-Spline Input Shaft
- Bronze Shift Fork Pads
- Dual Hardened Fork Pins 1-4
- Upgraded Low Alloy Steel Bearing Retainer
- Carbon Fiber Synchros
That should bring you around the 400 lbtq torque rating so keep in mind that anything above that will require a 26 spline input shaft.
From my own experience I would highly recomended you that you buy at least rebuilted transmission or up-graded transmission as often the used unit need to be rebuilted and will cost you more at the end.
Stock rebuilted transmission like the TR 3650 can be found for abouth 800$ to 1000$ while the up-graded tr3650 can be found for around 1700$
heres some tremec distributors:http://www.americanpowertrain.com/Tremec-Transmissions-Ford-Mustang.htmhttp://www.promotionpowertrain.com/1524384.html
Hope this helps