Having a head gasket go on these motors is less common than getting struck by lightning.
Me personally I use the GM LIM gaskets as they are a thicker aluminum. But the Fel Pro'* with the T on the end are also good. As for the plenum (typically the problem on an NA motor) I like the Dorman kit. Rockauto has them for under $80 IIRC.
Lower kit.. aim for the lower conversion kit. It'll have a ton of stuff and be lower cost than buying seperately.