4 high AND headlight relay mod!

[70c10guy]

Hi all, truck is a 93 c1500 with composite headlights. I've seen the guy on here selling his heavy duty harness with the 4 high mod that included a total of 3 relays. Doesn't look like he's available anymore so I was wanting to do it myself. I've done the Headlight relay upgrade on my 70 c10 and was pretty straight forward. I want to do it on my 93 but I'm not sure WHERE to add the 3rd relay for the 4 high mod. Do I add it after the relays on the light side or the truck side of the relays from the headlight relay upgrade? Super confused about this..