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“T-4”
I actually did not make a "T-4" part of my line for the 2007-  2014 GT500 with the 5.4 & 5.8 DOHC V-8, but have the  perfect alternative that can be found for right around $10.  This thermostat is made by MotoRad, under their part number  354-180, and can easily be acquired through an internet  search. It is also recommended by a well-known tuner, and  most likely sold by shops that deal with the Shelby. If you happen to have an O'Reilly Auto Parts near you, they  sell it as their Murray Plus 4138. It is still the same  MotoRad part, just in their box. My local store actually has  it for $12, and once you add the o-ring, it is a great deal! The only catch here is that this is a 180° thermostat. it will,  however, still make a nice difference over the stock 192°  version (Motorcraft RT-1185), especially with a good tune  and proper fan settings. If you want to save yourself some  cash, this is a great way to go about it. Although it may not  look the same as the Ford part (or Stant 49312), it is  dimensionally identical and will function exactly as needed to drop your temperatures!
GT500