How 'bout on your bumper like a winch? Not hidden, but could be fun!!
If you were a retard from around here, id tell ya to put it on your roll bar, but thats not a good idea
Seriously, under the hood is your best bet. You may want to just adjust them though. Aim them down towards the ground and forward, so the sound "bounces" off the pavement and infront of the bumper. This wont sound nearly as "muffled" as pointing them at your block, or radiator, or even up towards the hood.
something I have seen done with them is mount them on the inner fender, I realize that it becomes a tire obstriction offroad.. but try the inner bumper underneith the plastic tword the rear and see if they will tuck if not the bottom of the hood may work..
by the way on a h2 would be more fitting
If at first you don't succeed...
ya Odd, try to move the horns closer to the firewall, and aim them at the ground 3-4 iches before the rad. I had a bud with horns mounted like that. Shook the damn ground, and did NOT sound muffled if you were infront of them!
Just remember if you mount them directly above or below the cab you will have a lot of noise getting into the vehicle. It might be to loud and you will probably not like them. My personal opinion is if they fit mount them under the battery facing forward.
1978 CJ7, frame off rebuild, NV3550, Dana 300(twin stick with a sight tube), I6(258), Dana 44 Scout Axles with 4.09 gears, truetrac LSD. The rest yet to be decided.