Not really a mod but here is some stuff I keep in my truck at all time.
I have 3 tool bags that I keep in there
The first just has jumper cables
The second has 2 20 ft tow straps, 2 D ring Shackles, 1 tree saver strap(for a winch but I don't have a winch yet so I just use it as another strap) and one receiver D ring Shackle.
The third bag just has the basic tools in case I need them.
I call these bags my GO KIT
I also have a pair of coveralls that I keep in the truck just in case I have nice clothes on.