[BR3W CITY]

I think i posted in your other thread but I'll post here too. I'd start with a 6.0, as the most displacement will be your best starting point. Forged pistons for sure, then rod bolts at least (forged rods would be great too). Forced induction cam will be meeded, along with the matching valve train upgrades (springs, retainers, pushrods and maybe better lifters, to ensure you don't spit a needle bearing into your combustion chamber).
I'm not sure at what point the stock heads may get in your way. Most folks would also do a high volume oil pump while your in there.

You'll need enough fuel to run it also; twin 255's, or maybe something big like an a1000 pump. 60lb/hr injectors would be along the right lines also.

Turbo needs to be decently sized for a big single, you'll want to run an intercooled setup and possibly meth depending on what kind of driving you want to do, and how much boost you plan to run to achieve your goals. You may also need to consider running Speed density (no MAF) with the big turbo, as I've heard it can make tuning for big fi power easier.

The stock 4l80e will be a great starting point, but you'll want to get a properly sized converter for your gears and tire size to take advantage of the new power band.

This is only a starting point for ya, and I really recommend checking out ls1tech for more technical info on the topic. If you really want to see some of the boys making HUGE power (not all LS powered, but all eye candy) check out Yellowbullet.