Just make sure you have a good battery and high output alternator and you'll be fine. Spend the extra on a jump start battery pack with a good output. [I carry a 950 peak amp one] You'll find it will be MUCH more useful then a second battery.

I run a HELL ROARING Kit on my K5 Blazer. Ive got Red Top Optima and Yellow Top optima.. Here is how my kit works;

I set mine up so my 2nd battery is an Auxiliary battery (when choosing the kits it asks if its an aux or in line (parallel). I chose to have it as a AUX battery for the following reason;

If you have a parasitic draw or leave the lights on over nite, you will drain BOTH batteries. With the system I have, my AUX battery is purely as backup. I have everything wired to the main "starter" battery.

The kit includes Isolator and a 3 position switch. I have the switch in my glove box.

Down position - takes AUX out of charging system

Middle position (normal position)  - AUX is being charged but will have no draw taken from it.

Up Position - combines BOTH batteries for winching or extra power (still as a 12v system, just more of it)

There has been more than 1 occasion ive killed my primary start battery (lights on or parasitic draw) and just flipped the switch, combined the batteries and essentially started truck from aux battery.

You do have to supply / make your own battery wires, but it was super simple to connect. Got positive wire coming off starter to Isolator, and from Isolator to a BUSS fuse and then to positive side of battery and just ran a Negative from battery to frame. And then the isolator has 3-4 wires going to the switch. Their customer service is great, ive called them and they will walk u thru testing the system.