I would NOT use a amp supply cable as these draw lots of current so it will dip, when music whacked up, safer to use seperate supply.
The purpose of a rewire is to eliminate any old high resistance that may be present in the up to 22 year old wiring, on cossies, as any(DC) electrical motor(fuel pump) is VERY voltage sensitive and if it slows down your fuel supply gets low, sometimes low enough to do damage.
I put the relays on the area at the back of the nearside rear seat , up near the turret top as there is already a nice convenient 8mm hold there to hold the relay holder, AND if going to show or suchlike, you need only pull the relay for extra free security.
A group a pump at full chat draws 13 amps, so 28/030 is plenty big enough, I use 32/020 thinwall wire myself.
tabetha
tabetha