[gmc684x4]

Are thinking of rebuilding the engine at the same time ?
If rebuilding i would look at comp cams valve seal cutting tool to be anle to use newer style valve seals

Does the engine burn oil ?
Have you done a compression check ?

I can not answer site vendors Gmc Pauls are frequent answering questions

I use Rock auto and summit for felpro gasket sets i avoid the cork ones they dry out and are more prone to crushing from over tightining