I've got the motor in its intended chassis, so I can lend a few thoughts.
Either NA tranny should do fine, you'd be able to pick up a R154 on the cheap in solid shape. I'm sure you're already aware of the Getrag's clearing $6k+ as of late, and it'd be massive overkill in a sub 2k car that wouldn't hook up on anything short of tires borrowed from a pro-street friend and taking off the rear fenders.
I can't comment on the VVT-i, but I can definitely advocate swapping out to US spec turbos over their ceramic counterparts if you'll be running them long term. You'll be changing injectors and likely cams if you go much bigger anyhow, so that's less of a problem. I suppose you could always go old school and piggyback on the stock ecu if it came with the clip, but you'd need an adept tuner.
Personally, I'd leave the turbos sequential (at least for a while before trying TTC and seing if you like the change), and drive the piss out of it. The powerband would be much friendlier. (It's entertaining enough with 600+ at the wheels in the 3600lb counterpart - Once you break traction, the turbo sees it as free reign to pile on the power and try to swap forward ends.
) - part throttle at 130 snaps to near full throttle without changing much pedal pressure if the car goes sideways.
Check out JR's SR20 build, and where he went with it longer term. (changing turbo, adding Racelogic TC, etc.) I understand doing the 2j sheerly because you can though.
LQ Block out of a salvage yard Escalade with a few cheap used bolt ons would be a great way to get the LSX done on the cheap. (I've more than pondered it.
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Pictures either way.
- Forgot to add. I've seen a few R154's grenade, but it can be well argued you shouldn't be hard launching on slicks without preloading the driveline regardless of trans. I've got a close friend that managed to sideline a V160 on stock turbos and street tires as well. It's always good for a laugh, he's the only one I've yet to see that's managed to kill it in the fashion he did.