What are these parts for?
 

Trying to put my truck back together and clean up the electrical a bit. I traced the wires from the two boxes in the picture and one went into the harness, and all the rest were not being used. Prior owner replaced the engine, so I have no idea what he removed from the truck.

Here's a picture of what I'm talking about. Thanks

Re: What are these parts for?
 

I believe those are relays for the TCS (Transmission Controlled Spark) system. It was an early emissions system that retarded the ignition timing by blocking vacuum to the distributor except for when the transmission is in high gear and during a short start-up time.

Unless you're doing a 100% original restoration or need the system hooked up to pass an emissions inspection, you can either leave them unused or remove them.