They are early heads US and feature the large 49mm intake valves and 41.5mm exhaust valves and 39mm intake ports, 35mm exhaust ports. They are threaded for US air injection in the exhaust ports and can be plugged - we have proper stainless plugs with the correct thread and seal washers available if no air injection is used (not included). These early cylinder heads are date-stamped 9-77, and the date-stamps on 2 of the heads are not visible due to refacing them. They have all been refaced to the same height. Please check out the photos, this is a truly excellent set of big port 3.0 cylinder heads. These were…