About relays... My 96 Toyota has several and they aren't all the same. Bosch standardized them only to a point and I'm not sure what year. Mfgrs could still have custom applications produced so only their relay was plug and play. So that Bosch relay was sold out to tyco or somebody and could be produced anywhere on earth today, Who knows?
I know someone here builds a kit for headlight relays but I don't know anything about its construction or which relays used.
Mine is a 67 Plymouth. It's born with only 2 relays, for starter, and horn. I intended to add modern bosch type relays for high beam, low beam, and the one switched hot wire to engine bay that feeds ignition, charging system, electric choke, etc... I realized that the OEM horn relay could be the Bosch type also. The starter relay is much more than the typical 30-amp bosch relay is designed for. So keeping the OEM starter relay was no brainer. If the quality of Aftermarket replacements goes away, I'll deal with it then.
I built my own relay enclosure and placed it near the right frame rail and alternator. Today it holds relays for high beam, low beam, horn, and engine bay. Just aluminum channel supporting several relays under a plastic cover. There is space for electric fuel pump relay, a/c clutch relay, whatever I decide to add in the future. Every relay there is identical/interchangeable. So while I'm modifying the OEM wiring harness for 60 amp isolated field alternator, electronic ignition, and more, I did spend the hours to modify OEM wiring diagrams, print them and put them in the car.
The part I impressed myself with was labelling the harness connectors on these relays. If the low beam relay should fail, I can move that connector from there to horn relay and forfeit the horn for a while. If you use a box from parts yard wherever its labeling could be wrong.
Nylon bolts and nuts from a toilet seat hold the cover over relays so only a flashlight required for roadside repair.
Only relay located inside the cab is mounted by the fuse box and feeding the amp in the trunk.
If I had been rewiring the entire car as you are, I probably would have gone with Painless or similar. My plan was modifying the OEM harness while keeping the OEM wiring diagrams and wire colors for the future owner. And there is a underlying reason I care about the future owner. No need to go there now. Good luck with your build.
Yeah, I had to put my engineer's hat on and think it all though.
