don't reuse the 2.8L block/heads! they are inferior to the 3.1/3.4 in design and construction quality. Start with a 3.1/3.4 and the reuse your intake/exhaust/accessories/trans/everything. any year 3.1/3.4 from a Camaro/Firebird will work (I think the S-10 had the 3.1 at some point around that time). I think they were early 90s but unsure of the exact spread that used the 3.1/3.4. car-part.com might help in the junkyard hunt.
there should be a thread or 2 in the DIY forum (which isn't organized yet). the big differences are that you'll need to add an inline electric fuel pump (the 3.4 doesn't have any boss for the 2.8's mechanical pump) and the flywheel needs to be neutrally balanced (the crank of a 2.8 is not balanced on its own, but the crank of a 3.4 is).