rdavid, i am gonna take a stab and say that grigg will tell you the 4-53 is an outstanding engine as from reading through alot of his posts it seems as though he has had some good luck with them, one thing to consider about the 6.2 or 6.5 swap that some people might not tell you involves teh injector pump.... i am a general motors employee and i will even tell you that they are garbage. there is a reason when you spend the $ to have the dealer install a new one it has a 10yr 100k warranty.... you'll need it and GM knows it so to retain there cust that have that set up they offer a warranty like that, that you more than likely will need to take advantage of.. just another $.02 from me though
~army truck
