Heard from JimP (thanks Jim!) where he got his wiring for firewall forward, so I ordered 10' each of red and black from here.  That should be more than enough.

Also, got some red and black heat shrink tubing here.  The 3/4" should fit snugly (ordered a quantity of 2 each color), but I also got some 1/2" (ordered a quantity of 1 each color) in case I have some smaller wires that need covering.