What gauge/size chain is used on the turnbuckles?

My TorkLift set up came with springs only on the two front ones. You hand tighten till there is 1/8 inch of possible travel for the springs.

The rears you bring to a hand tight level. I go a bit less because the threads on my sailboat turnbuckles are not tapered as much as course threads. Fine threads afford a bit less effort to tighten at the right tension.