Hotflash, if all you want is to work the starter use #12 or #14 wire and all you need to do is tie into the starter selonoid. One side to the battery connection and the other to where your ign. ties in (red wire) to the selonoid. The switch should be a momentary type and you will still need to turn on the ignition switch (key) to "start" the engine. The momentary switch will spin the starter any time you want, in fact it is exactly how I start my engine whenever it has sat. That way I am looking at it when she starts and I can do a visual check for leaks.
Dave Neptune