1991 Toyota pickup. Motorhome..1 Ton. We want to convert the existing incandescent sealed beam headlights over to led. Can you buy the H4 3 Prong harness with spade plug inside. To use with existing harness plug? Or do you need to buy the whole conversion harness with Relays and fuses etc

 

No need to change wiring, unless you want to refresh the old connectors.
Try to find Trucklites 27450C. Not polarity-specific so plug-and-play into Toyota's switched-ground system.

My actual installed lights on my 1986 4Runner here:
https://www.yotatech.com/forums/f131...l#post52311149

Actual install on my 1996 Hilux LN106:
https://www.yotatech.com/forums/f131...l#post52504240

I believe it is now being sold as Eagle Lights 27450C.
Cheers!