First off I'm going to assume it is a 2 piece seal engine with the perimeter bolt valve covers......they are all the same basic engine but with different cams. I don't know how you would know what cam you have unless you pull it out. My crew cab I just bought has the 250HP 10067353 crate engine (luckily the PO kept the receipt for the engine)
http://www.jegs.com/i/GM+Performance...67353/10002/-1
then there is the 290HP 12499529
http://www.sdpc2000.com/details/gm-p...parts/12499529
and a 300HP 10067353
http://paceperformance.com/index.asp...&ProdID=264227
if you notice in the specs they all have the same basic specs (block, heads, ect), but with different cams.
can you tell I have recently been researching this for my engine