[bigblockv6]

In 1968 GMC switch over to a valve cover type breather/filter that has a hose and tube that attach to the bottom of the air cleaner. There is no filter on the back of the engine as it is permanently capped off with an expansion plug so there is no need for one on any 68 and later V6. As for the oil filter the most common was the shorter AC PF24 and then the longer AC PF30 which crosslinks to the Fram PH11. On my 68 K-2500 for more capacity with a 478M V6 I use a longer 7 inch Wix 51831 or NAPA 1831 Filter which is for hydraulic pump equipment but it is exactly an automotive engine filter. There are many variants for the spin on oil filter for the V6 and the good thing about is Pontiac, Buick, Oldsmobile, Cadillac as well as AMC/Jeep from the late 60's into the 70's all use the same or compatible oil filters with the GMC V6.