727 transmission questions

The 360 will have close to 400 HP so it's no overly powerful. So it would be better to just upgrade it? Would the overall cost to built it to handle the power be similar to the 727? Because I doubt the 904 in it's current form would be able to handle the power reliably...or am I wrong about this?

And I have to shorten the driveshaft anyways, my car has a 7.25 rear end, I don't think it would be too happy behind even 250 hp!