Does anyone know the horsepower rating for the Allison MT-40 Trans? My '71 came with FORD documentation that shows the 391 is putting out 140hp and torque at 271 ft lb. The Alison documentation that I have is for a MT-640. This documentation shows that the MT-640 can handle up to 250 hp and up to 480 ft lbs of torque. I am about to make some modification to the 391 and I definitely don't want to overpower the trans.