I'm not trying to be debbie downer, but as someone who REALLY tried to make the IRS work, it's not worth it if your goal is to launch hard and do the 1/4.
If you go to auto, you can probably keep the IRS assuming it's built. If you have a turbo, you can probably keep the IRS assuming it's built. If you don't launch hard and want to keep 60's in the high 1.4's to 1.5's, you can make it last.
If you want low 1.4's/1.3's or quicker, here is what happens when you have a blower car, IRS, and 6 speed. You break. Constantly. Your "built" T-56 will break the output shaft unless you upgraded that. It will happen on a hard launch if you have a built IRS. I promise you that. Your IRS is going to need half shafts (the G force half shafts are by far the best on the market, they aren't going to break), a diff cover with preload bolts (this is going to save your main caps and all kinds of other parts from breaking, including to a point, the center section), a center section (this is the next weak point), then you are still going to break the inner workings of the 8.8 (ring gear, spider gears, clutch pack will need to be upgraded to something like a wave trac, etc).
IT ISN'T WORTH IT. Either don't launch hard and be happy with 1.5's, or go to a solid.
thanks for the input. your point is extremely helpful and is swaying me to consider a solid swap as i only drag race.