I did exactly what
@crackedback recommended. Ground cable comes off the battery and goes straight down through the trunk floor to the right rear frame rail. That cable can't be more than 14" or so. Then a same size cable from the right rear cyl head to a nut welded to the right front rail. Again, not very long. And I used either 2/0 or 1/0 welding cable (can't recall) for the positive side...of course through a Ford relay to keep it dead except during crank.
With a mini-starter, the avatar's 10.5 CR 408 will crank like crazy if need be although it normally starts almost instantly. I give
@crackedback the credit for my setup!