I have WK sliders, I can't say for sure but I'll order a set of your gussets before the weeks out and find out one way or another (not concerned if I have to modify something)
It's probably just me but I'd ask him about anything else he may have touched while owning the thing because anyone capable of doing any/all of that without noticing whether in a hurry or not I'd worry they were capable of turning the ignition key the correct way to start the truck let alone...
All of those connectors you have pictured would go to the ABS module, I don't know if these things came without ABS or not as an option but if it was supposed to have ABS and someone deleted it it's possible they didn't do it right or it's never been bleed properly since deleting it.
Given the...