"If you look at that motor without the cover on it looks more like an LS1 then any northstar I have ever seen." Because it's longitudinally mounted, it has aluminum heads, a plastic intake, and wiring draped over the heads. You need to get out more.
"It might be 80% new the same 80% new the C6 engine will be." No it is not. It's the same 80% new that the SRX engine will be, because they'll share an engine. XLR and C6 will not share an engine. It's just that simple. It's a fact. It's been published. There are a lot of sources of information. You might try reading something some time.
"You must not remember the late 1970s and 80s when GM engines were interchangeable." I remember it quite well. It doesn't change the fact that what's sitting in the XLR engine bay is the next-generation Northstar engine exclusive to Cadillac. Did I mention that you need to get out more?
"Just what kind of motor do you think is in the Escalade?" Oh, you mean the truck? A truck motor -- the intake and programming of which is exclusive to Cadillac, by the way.
You know, your lack of awareness of well-known information is amusing. I withdraw my recommendation that you get out more.
.Jinx