318 0r 360

The 400hp is just an estimate, i needed to know if the tranny and rear would hould up to that much power. I want it to be no more than 400, but no less than 300. This is why i am going back and forth with the 318 and the 360, i can probably acheive the lower end of the power with the 318, but i may have to spend more money, to get that power from the 318, than i would with the 360, again the issue of mileage is still in question. As you can tell i am very indecisive right now.