Can't answer for them directly, but indirectly I can say do it wherever it's convenient.
It won't really matter in many cases, although putting them near where most of the electrical connections are might not be a bad thing. Or just anywhere, to also help reduce radio noise interference overall.
So just a convenient spot in the rear, for the tail lights, side markers and such. The frame is the ground for the rear tank sending unit, so that could be an area around the rear wheel well and frame member.
In the front, I've done it between motor mount bolts on the engine side, to the frame near the engine mounting tower. On the full-size trucks, there are a couple of very convenient bolts already there.
And while you're at it, add a braided strap between the back of the engine and the firewall. Here again, convenient existing bolts are perfectly fine. If you want it more out of the way, you can make your own bolt location. And even perhaps pass it through so that items under the dash can be grounded there as well.
In lieu of braided straps (which are easy to find at the store, or even make out of a roll of braided strapping) you can also use some Black wire. I always use 10ga for this, but you can use 12ga if that's what you've got handy and want to get rid of.
The smaller the wire gauge, the more grounds you might want to add. But unless you're running an electronically heavy Bronco, a few well placed 10ga wires will do the trick.
I forget the rating, but a typical braided strap is usually a much higher "wire gauge" size than you might think.
Paul
