I only have one of those 24" grovers, and like I said earlier it's on the front of the front crossmember behind the bumper. I had to take the bumper off to get it there. If I had a 2nd one, I'd put it behind the front crossmember pointing exactly opposite the first one. I have installed my horn on 4 different trucks so far and it will fit behind or in front of the crossmember so you'd end up with one in front and one behind the crossmember. Both would be pointing sideways, one to the driver's side and one to the paggenger's side.
Hmmm, I've been thinking about getting some train horns, I wonder if a 2nd grover would be enough to satisfy the urge to make more noise...
Good luck,
Mike