What about using the cage/roll bar, if you have one, as a ground medium. Weld a stud near the battery, another on the A-pillar Bar, snout bar or door bar and connect ground to engine/frame at front.

If you use a ford/remote start solenoid, you don't need to worry about that honking 1/0 or so wire being hot all the time and require a fuse holder. I prefer it be cold any time except in start mode.

There are a bunch of ways to wire the car with a battery in the trunk.