use a 1800 or something up front (whatever fits) one or two 2400 or whatever your budget can fit for 1800+ in the back (all 3 kinetik). Buy terminals that will fit two 1/0 wires (or rig one yourself with crimps) and run two wires for each post to the back of vehicle. Attach to you batts and then to amp.
I would start with 2 batts and then move up to 3 if there are voltage problems. The alt is only if your voltages constantly dips into the 12v range. There is no need to run 2 alts for only 4kw. that one alt will be sufficient for perhaps double that(just a guess).
the mechman website
Kinetik website
The kinetik website says you need two HC2000 batts
You can pick them up for cheap at millionbuy.com