Um, that should do it for you! Make sure you don't forget the supporting mods, i.e.
tranny, clutch, axles, differential, SFC's. I'm not too sure how tough the axles are with the IRS though.
The 99' motor has the same crap rods and pistons as the GT, so it's not gonna hold the power he is seeking. Plus I think the "fix" had something to do with the intake manifold, which would be out of the picture with a roots/twin screw style blower. I do agree $15k is ALOT. The block and crank on the 99' motor will hold a ton of power, it would be much cheaper to forge the rods and pistons and then throw a blower on top.