Well the main reason for looking at the 400 was in the future I will be going procharger and looking at 1800 hp at the motor so not huge horse power but more than i think a 727 would handle. I've got new 1st and 2nd gears ( reduce the SLR) for my current box and after talking my trans guy we will be going a billet output shaft as well. Unfortunately i have already put a lot of money into this box so now the new gears have shown up i will stick with this one. I wish i had done more research when i got this motor together and went to the 400 first.