snip... I'd do it that way for a few reasons. Personal rig is a 2a so I have none of this fusebox inside the cab nonsense. I'd rather pop my head into the engine bay than fiddle behind/under the dash. I want to up the wire gauge to the headlamps to take maximal advantage of fitting the relays...

The feed for terminal 30 could certainly just be a single wire that is split/Y'd at the relays and used to feed them. If I were doing this without any other wiring changes I think I would get relays with waterproof and fused housing and mount them on the bulkhead near the existing 3 way bullet...

Basically any Bosch type 5 pin relay will do the job. 12v bosch relay would be your search term or request at the parts counter Or you can by inexpensive kits off ebay or amazon, either as a relay harness or as a generic headlight wiring harness that may or may not fit properly...