What's the max with this setup?
 

With a stock LS1 block (3.905) forged rods, & pistons and a GT42 - intercooled, what would be the max HP this could support assuming there was plenty of fuel?
The turbo supposedly supports 1100hp.
Weak areas preventing higher gains?

you will need some good valve springs and you might as well stick some head studs in there. other than that i think you could max that turbo out without damage as long as you have good fuel and a good tune.

Have good spings and studs already :D

1) Money
2) Ability to safely tune that combo in the 650-800rwhp range
3) Fuel system

Would the stock ignition/coils hold true closer to 4 digit horsepower?

yes, at least the square truck coils will. i had to up my dwell to clean up a top end miss and you do that thru programing.