Re: next mods for mo powah???
It's going to be tough to get big gains from where you are right now. Two things that come to mind are the cam and turbo. You've got the popular 415 cam but in my opinion it's a pretty lame cam to race with. Look at the specs:
http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=569&sb=0 - it's only a 210/215 cam, which Comp rates up to "5000 RPM" and says "Works with throttle body and sequential port injection with aftermarket chip. Good low end and mid-range."
The cam is popular because everyone likes to play follow the leader instead of truly optimizing their combo with a custom cam. But this cam is designed for 15 second N/A S10s, why would it be the cam of choice in a 600+HP turbo application?
I've got basically stock vortecs and a custom Comp 218/218 115 LSA cam with their XFI fuel injection cam lobes. It seems to make good power to at least 5400. If you have the tuning capability (and I know you do), you could try something as big as a 224/224 like the one TurboTime sells.
A cam swap is a lot of work on these trucks, I just did one last fall with full accessories and A/C (I posted photos of how to move the condensor without disconnecting it) and I bet you're only talking 20-30 HP gain.
I am one of the last people to recommend "big turbos" but in your case since you're already at 26 PSI boost with the PT61, you stand to gain some decent HP by switching to a turbo optimized for the high boost you plan to run. How high of boost can your octane support? Find a turbo with a compressor map that's happy in your desired area. If streetability is important, the PT6780H a.k.a. the "PT67GTQ" is rated near 780 HP and has gone 10.2 @ 131 in Phil Long's Syclone (with 415 cam and ported vortecs) at 25-28 PSI boost I believe.
PS: I also run a Yank converter, a custom "PY3400E" at 2700 RPM stall. Here's a
video of my tach during a boost launch: