There is an LS2 in it right now, Bob Lutz posted on his web blog that they ‘Have an extra 100 proven hp available if we need it’ aka LS7. Basically it will get what the Vette gets, rated it down 5hp and put it in a slightly heavier 4 seater car, nothing new here, that part works very well.
Platform is an interesting subject, you cant just call it a Zeta. It has been sort of rumored to be on Zeta, Zeta-lite, Sigma, Sigma-lite, etc etc As Scott Settlemire said, ‘Zeta is just a name’
And yes, IRS rear. I guess there needed to be something in there to make import guys happy and me angry, so there it is.