The main negative battery cable almost always goes directly to the engine block. In the case of the original Ford set up, it was a bolt near the front, under the alternator area.
If your block is equipped with a threaded hole midway back along the pan rail, closer to the starter, that is an even better place to mount it.
Since the starter motor is the heaviest load on the truck, putting the ground closest to that is a good practice.
You must also have at least one to the body, if not more.
Ford simply spliced a metal clamp into the middle of the battery cable and bolted it to the inner wheel well. Since aftermarket cables don’t have that feature, add your own ground, of at least 10 gauge wire, from the negative battery cable to the body somewhere nearby.
A common spot is one of the attaching bolts holding the starter relay/solenoid to the wheel well.
A secondary ground that never made it to Bronco production, but almost every other vehicle had towards the end of our run, is to add another one (you can use the same 10 gauge wire) from the back of the engine to the firewall.
This gets it closer to the dash where a lot of electrical hanky-panky goes on.
I don’t like using an intake manifold fastening bolt, but there are other places near the rear, such as for the throttle linkage, and bell housing bolts.
Wherever it’s most convenient.
