I totally dig the idea of a welder. i had that idea a few times, but in the end i decided it wasnt a necessary add on for my truck. i am dealing with confined space as it is anyhow and the reality of it is that i will probably just drive my truck and pull trailers once in a while. it wont ever be for serious work... haha i am already planning the 'for everyday use' build on my yellow truck so i dont have to drive the spiffy one everywhere if i dont want.
those relay holders are this
https://www.alliedelec.com/te-connec...1002/70199126/
they work with the normal 4 or 5 pin Bosch/Tyco relays. they do require a certain double crimp terminal to lock into the holder. they are linked in the lower part of that web page. they interlock so they can be mounted in a gang like i did, or they can be mounted individually.