The car motors are aluminum block, came in Corvettes starting in 97 and V-8 Camaros and Firebirds starting in 98. And in GTOs and Cadillac CTS-V until 2004. Then in 2005 the LS2 came along which is called Gen IV because of some subtle differences mostly in sensor and their locations. The 97-98 motors run good but have differences than the later models. Trucks started getting the motors in 99 with the 4.8 and 5.3 liter, These were iron blocks and I think in 2000 or 2001 started getting aluminum heads. 6.0 liter came in the 2500 and above trucks and then in the SUVs. The 6.0 are designated LQ4 and LQ9. The LQ9 is in the higher end SUVs and has higher compression. That's a very brief description. Mixed in there are the crate motors and the newer LS3 6.2 and the Hipo 5.7 LS6 and super high end 7 liter LS7.

Hope that helps

Pat