IMO, Stage 3 Hybrids are pushing a 38r. It is a lot of fun to drive, but more air would be much better. A modded H2E or GQSSB from WOP would be best. I am in the process of putting a GQSSB on mine here in there next two weeks.

 

For a solid Transmission, BTS is somewhere around 4500 plus your go fast parts so yes, the budget needs to increase significantly for 500 hp...

 

The 38R is really fun to drive with large injectors, but at higher boost levels (40+) its just out of its range... A 1.15 housing can really help and thats what I ran, but I much prefer a T-4 or T-4i midframe turbo over any drop in.

If your goal is 450hp, and no more then 250/100 injectors, I think you would be fine with a 38r and a 1.15 exhaust housing.