I ordered the petcock rebuild kit from Murph. I did two a few years ago on two other C-10s. Now my dad's is dribbling. I can't remember, does his kit come with he oval shapped o-ring to seal it to the gas tank? I shot him an email but haven't heard back.
Edit: The answer is YES, it does come with the o-ring, it is just not exactly like the OEM.