Grant, Is there any option to get the original setup from the '55 270? Gmc's either had the road draft/oil fill combo combined with a vented rocker cover or a crankcase air intake/oil combo with a "sealed" rocker cover that had a bulkhead 90 which went to the pcv valve and intake valve. In my opinion the pcv setup is preferable. But either will work if you have a vented rocker cover for the road draft. I don't like the road draft on the gmc's because the air drawn in to replace what is "drafted" out of the crankcase is not filtered through the rocker cover. Dust can migrate in there and give moving parts and the filter more work and wear. The pcv setup has an oil bath filtered air intake so that incoming air is properly filtered. Additionally there is always positive ventilation even at idle if the pcv valve is properly working. Don't throw any of these parts away or modify them, both setups are getting a little rare. Too many old trucks are being cubed up for shipment to China these days. grin