[Tx Firefighter]

A1 Cardone lists both options for your truck at Rockauto, o ring and flare type. I catalogued it for the 79 model C10 with Olds diesel that is listed in your signature.

O ring seal type is a 527252

Seat type seal is a 527918

Price is 142 dollars including core charge for either of them. Both are also in stock. Cardone shows both of the choices fits 1979-1980 trucks only. You'll need to make sure which one you need and choose the appropriate number above.