Intake gasket troubles 5.7

I have a 97 suburban that had the lower IG replaced on last year. Now it is burning antifreeze again (smell it and see steam bad from exhaust) Also when I try to start it sometimes it is locked up. Could this be from antifreeze getting into the cylinder? I also have a 97 z-71 I bought off a guy who took it to a Dealer that told him the engine was blown. I bought it from him(original owner) for $300.00 :smokin:. Dealer told him that #6 cylinder was missfiring and needed a rebuild. A friend figured from the air sucking sound that it was the gasket blown over the # 6 cylinder I fixed it and the truck ran great for 3 days then started knocking bad. I was told maybe that antifreeze got into oil and ate up the main bearings?
Anyway have 2 question,
1.On the suburban do you think that it is the intake gasket again? It has new waterpump,radiator and cooling system (pull a 22 ft bass boat 5,000 miles a year.
2.Im looking for a block to rebuild on my z-71 and use all the rest off my old motor. What is the year exchnge for the vortech blocks are? a friend is telling me I can use any 5.7 350 block no matter the year? Thanks for any help