In these photo galleries you will see the differences between the oil filler necks used by the street 914-6 and 911 and both the racing versions of the oil filler neck used by the 914-6 GT and 911 race cars. The racing version oil filler neck of a 914-6 GT is an important and integral part of its Oil-Cooling and Lubrication System. See links below...

914-6 GT Racing Oil Filler Neck, OEM NOS: https://pbase.com/9146gt/9146_gt_oil_filler_neck_original_nos

911 ST / RSR Racing Oil Filler Neck, OEM NOS: https://pbase.com/9146gt/image/48159560

914-6 Street Oil Filler Neck, OEM NOS: https://pbase.com/9146gt/9146_gt_oil_filler_neck_9146_oem_nos

911 Street Oil Filler Neck, OEM, Used: https://pbase.com/9146gt/9146_gt_oil_filler_neck_911_oem_used