I'm looking Amazon and so far I haven't found what I would like to get to add the extra functionality I would buy, found other idea and adding them to my 'wish' list. My truck has a second battery tray, one of the Carfax's that was provided by the dealer I got it from, said it was used as a fleet vehicle in Chicago when it was new, so I don't know if that is why the second tray or not.
I like the idea of the big 3 upgrade but I haven't seen the need to do that yet, that was why I ask the question earlier of how much of a difference it made on a mostly stock truck. If I ever get around to it I may try to find some of the grounds and clean them up.
Years ago I got a 1977 pick up truck from a private individual who had done several engine swaps, so to make it easier on himself, I'll bet you can guess what he didn't bother to make sure was reattached, yep, the grounds. The ONLY one that was hooked up was from the battery to the engine block. It had a trailer hitch wiring in the back and when I would check it, it had around 9 point something volt back there, once I 'discovered' the lack of grounding and fixed that, yep over 12 volt back there.
With all that said, I will probably just try and find some ground wires on it and make sure they are good, for now.