I carry a 10 ton Hein-Warner bottle jack and a couple of 8" pieces of 2X6 and 4X6 blocks.
I made my own jumper cables, they are 25' long and are #2 welding cable. They are terminated with 500 amp parrot clamps.
I made them 25' long so I can pull up behind someone and the cables will reach instead of having to park next to them.
I kept the cables seperate because 50 feet of #2 is getting kinda heavy.
I have watched a big wrecker try to start a class- A coach with 330 cat and they could not start it. I connected my cables and it started right up.

 

I have a Harbor Freight $39.95 on-sale, 2 ton floor (garage) jack (not the little lightweight one hand ones, a genuine 40# floor jack) chained down in the bed of mine for the last several years. Works fine for my truck unless I have a big load on.