I needed two light assemblies (which come with gaskets), one WHD1 harness (which comes with two bulbs), and the clip set HW1801. No need for gaskets HDTSG or bulbs BULB53 except as spares.
Installation required loosening the trim rings so the light assemblies could slide into position. Push in the bulbs, fish the harness, install clips, secure grounds to hood & firewall, and plug into the connector. Everything worked perfectly.