I keep mine in the back cargo area between my two big junk boxes, along with a 3' prybar and a couple of spare shafts...I don't have a back seat in the way though.
IIRC Goatman made mounts on the front bumper beside the winch that mounts it horizontally at or just above the front hood level. 1.5" square tube pedestals and some flat stock IIRC
MarkWNC (and others) have theirs mounted behind the spare on the swing-out carrier.
I've seen folks mount a 48" inside the driver-side rear cargo using the mount for the OEM spare tire....kinda angles forward, and might be in the 'headache' zone for a rear seat passenger.
Of course there is always the roofrack (if ya have one) and Hi Lift makes a spiffy lockable plastic case for them... I forget who had one of these I've seen...A Mechanic? Motorman? 2Offroad???
My last choice would be on the leading or trailing face of the bumpers...seems like they'd get maulled by rocks, and possibly wedged in a bind, and of course that would be when ya needed it the worst
Wherever ya put it, do some homework in anchoring it down...it's too big & unfreindly to trust with generic bungee cords (at least use 550 cord & duct tape)