I've got to point out.....I just had chills. Reading through....re-reading out of curiosity....I had this flashback of a 2008 thread.
We were discussing - almost identically as we are right now - how Chevy should put the L76 (361hp) from the then-current G8 GT into the base V8 car, and the LS2 (400hp) into the upper-trim.....
Instead, we got an LS3 for "cheap", and an LSA in our upper-V8 trim.
I'm hoping history repeats itself!!
My only problem with this concept of a base model 5.3L is cost...it won't be any cheaper to produce a 5.3L than the LT1...not if we're assuming it uses all the same tech.