FelPro first design didn't have pins for the rubber end pieces because 96/97 blocks were cast w/o any pin holes. 98+ appear to have them (TMK) and the only thing is does is help hold the end rubber piece in place. Second design had the pins on the rubber end seals. Fel Pro is still using the plastic gasket though.
The GM dealership ones will have the pins (aka second design) and be made of aluminum which to my experience is holding up perfectly.
Part number.. Here'* a link to all the common parts we will usually see
BonnevillePRO.com • View topic - Common Part Numbers