Quick list - front main, rear main, oil sump, timing cover, and valve cover. Especially if the engine has been sitting for a while - these gaskets tend to dry out and shrink, which causes leaks.
Even if it's the early engine, use a 1996-up oil sump gasket - it's one-piece moulded rubber, which makes it far easier to handle! (OK - it's apparently not. Probably useful advice for others, tho...)
While you're getting the other goodies, pick up a set of SB Chevvy valve cover studs (for cast covers, they're a bit longer.) Install four in the oil sump rails, and four in the valve cover holes - widely spaced. They'll help you keep things under control while you're putting it all back together.
Get new engine mounts - you're going to have them exposed anyhow.
Tag all electrical and vacuum connections before you disconnect them.
Use LocTite #242 on the screws for the flywheel/flexplate to crankshaft, and for the torque converter/clutch to flexplate/flywheel. If you've got a manual, it's a good idea to replace the pilot bushing while you've got it out - even if the clutch is in good shape. The pilot bushing/bearing isn't always changed as part of the job, and a worn bushing/bearing there can cause all sorts of trouble. May want to change the throwout bearing while you're about it - cheap insurance (and you'll kick yourself if it needs to be done in a few months...)
That's all I can think of offhand.
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