Borg warner upgraded the t5 that came out of the mustang to cope with the extra torque but probably still "only" good for 450ish depending on how hard you drive. Tabetha used to always say the t5 was only rated to 180lbft but that's bull shit, maybe he's confused with the mt75 that I can believe being only capable of that torque as it's basically a 4x4 version of what comes in a dohc 8v sierra.
I don't get any wheel spin but I have a de-cambered back end and without this hardly any of the tyre touches the road, I want to get a good beam next more for handling than anything else as it's all very twisty roads round my way.