I mean, you dont NEED To use a relay kit but the reason its done is to enhance the lifespan of the switches and to provide less potential for things like voltage drop and increased lengths of high amperage runs which is only a good thing for the long run. If you dont want to mess with it now and make it future-yous problem, thats fine. (We all do this in some way)
your right in the long run...for me the old stuff as run for 35+ years and with the better technology of today motor (i see video with just changing the motor keeping the old regulator work fine) i think that will be ok...but shure adding the relay kit is a big plus!
I’m not a square body expert, so I might be wrong. I don’t think power windows were available until much later in the production run. I remember somebody here doing a window conversion and finding out the cab and doors weren’t marked for the wiring boots.
You could use a typical 5 pin relay instead of the factory part. Instead of power coming off the fuse in the fuse box, use any run/accessory powered spot in the fuse box to trigger the relay