Charging system and other wiring change help needed

No replys on the difference between the ford relay and a continuous duty relay? Anyone?

If #10 wire is not big enough for the ALt to trunk run will #8 be big enough. I am having trouble finding #8 without having to buy a 100' roll. I can buy #6 @ $2.19 ft but is that over kill and more of an expense then I need to go with?
Where is a good place to buy #8 if that is heavy enough. When I searched the web I didnt find anything except for sound system lead wire and I didnt think that was the right stuff. Thanks
Rod