Monaro never came with a LS3. 
Early cars (CV8 and VXR) are LS1. Facelift CV8 is LS1, but the facelift VXR has a LS2. 
 
  
My mistake still not 15k slower than than a vet 
 
  
It isn't all about speed. 
  
I am currently weighing up the pro's and cons of getting a C5 or a Monaro. Both LS1 engined, both just as fast as the other, both circa £10k, but hands down the C5 is a better looking car. 
Only reason I am even considering the Monaro is because of the back seats.