I've worked with guys with Gen3's twin turbo's. Stock blocks seem to hold to about 1,400 before cracking the lower end of the bores. Had some issues with the high dollar cometics not holding up over 25 psi boost. With .570 stock lift, wasn't a stretch to get the valve train trouble free. Caps didn't seem to be an issue. But I'd rather see a bigger bore and shorter stroke. Start with a 6.4 block or an aftermarket block, if allowed. Stay away from the 6.1 block. Not as strong as first thought. 5.7 block ended up being the stronger of the two. I've seen a bunch of sheetmetal intakes exploded from backfiring, so I would stay with cast. Eagle or Apache heads would get you there, I think Eagle the better of the two for strength and availability. Bunch of aftermarket heads and intakes are becoming available now. I've used MSD Hemi-6 stand alone ignition. Works well once you understand the graphs.