[Lloyd-TX]

The #64 cylinder head is a great D-port head, on a 455 or larger engine. 87CC chambers, 2.11/1.77 valves and screw-in studs were all standard fare. Great setup for a pump gas 455+ engine.

Two downsides - it's a farely uncommon and sought-after casting so be prepared to pay for a pair.
The only other issue is that there is a boss "missing" from that casting (and all pre-1971 castings) which allows the use of '71 and later alternator and accessory brackets and pulleys. One can run the later accessory setup without that boss - which has a threaded hole for the alternator thru-bolt, but this destabilzes the accessory mountings and can cause belt flipping or throwing.