96+ Vortec 5.7 in my 71 Cheyenne

[Tim240Z]

For various reasons (which I won't bother going in to), I need to convert my truck to squeeze as much fuel mileage out my truck as possible.
I am currently running a rebuilt (by me) 350 with vortec heads and L98 Vette cam grind and RPM performer intake and 750DP, and TH350.
I've considered just putting in a OD tranny, but after much soul searching, I've decided to transplant with a 5.7 Vortec out of a 96+ chevy truck or sub.
I've searched through pages and pages here and found a little info, but nothing really substantial.
I have no problem with the conversion, it should be as close to bolt on as can be (done an LT1/T56 in my 240Z , as well as many other conversions).

What I am looking for is info on any particular issues with engines that I should look for....reliability issues (I saw something about intake gaskets), any idiocincracies with the engine/tranny that I should be on the lookout for.

Thanks,
Tim