By don't use the head gaskets he means:
Buy the top-end gasket set from a GM parts dealer (any dealer will do).
The package will contain various gaskets for the top end of an engine (this will include the head gaskets, and the intake gaskets etc) BUT by 'dont use the head gaskets' will means you won't have to use them because he is recommending you not bother taking off the head, and replacing the gaskets, he is saying to just do it all EXCEPT head gaskets (dont even take off the heads on the car!)
BUT if you really want to put in new head gaskets, then by all means use the GM ones that come in that package, they are the best for your Bonnnnnnnnnnnnnne!
87 Pontiac Bonnevile!!