Latest from Chevrolet: https://www.chevrolet.com/performance-parts/transmissions/8l90-e-lt1
Weight shows as "210+" pounds. I take "+" to mean the weight of the converter and fluids. It might be in the vicinity of 35-ish pounds (just a guess on my part.)
But the specs are very impressive, especially coming from GM, which is very conservative (and rightly so) for their transmission claims. But also as expected, you can't just connect it to any motor: it only fits the GEN V LT1, LT4 or LT5 engines. As we rightly judged, the intricacies of matching the transmission operating parameters to the motor are too complex to easily permit adaptation to just any engine. No doubt some adventurous types will try to crack this and re-program it, but they had better be as smart as GM or they will likely compromise the life of the transmission. Torque management is very likely part of the secret sauce, and you've got to be able to control throttle and/or ignition timing to make that happen...
The appearance of the sheer size of this thing definitely suggests that the transmission tunnel in the MCSS body needs to get a lot bigger in width and height for this to fit.
Me, I'd save most or all of the 245-ish pounds of weight and go with an electric drivetrain.