For sure the add on harnesses are great to help with aging stock harnesses and voltage loss....but the stock wiring is 100% plug and play with an H4 bulb and housing.If you buy the 80/100 watts h4s, you should get the relay harness too. The heavier wire that delivers a strong 12v from the battey will give your new bulbs the power they need.
maybe true with 50/60 watt but why bother with 80/100 if your not going to go with relays, heavier gauge wire and 12 direct from the battery? To the OP, go ahead and get the lights and lens, but if like Seth mentions in step 1, you have dim lights that get brighter when you rev up...then you can always add the harness later.
I am currently framing a new garage/workshop with hope of having a useable space sometime this winter. I'm thinking to pull the harness out of my 1988 FJ62 and lay it out on a board with all the components so I can have a virtual truck to play with. I'd like create a harness kit that replaces the stock kit without being an oddball add on that just clips into the stock headlight connectors.