If you want 450 now, you will probably get hooked and want more later.
If you plan to run a single turbine, then a T72 would be the way to go. At 450 horsepower @ 5500rpm, with a BSFC of .5, a VE of .8 & a charge temp of 185f you need 12psi @ 45 lbs/ min flow. That is a pressure ratio of 1.8
Plot the point on that map where 1.8 & 45 cross. Keep in mind that the center island in that map is the maximum efficiency for that compressor. The curved lines that cross the islands are turbine speed.
B.