With your fab skills I'd recommend under chassis headers and then cut the floor behind the driver seat for muffler clearance. Then you can build a super nice exhaust system which is high flow, fairly quiet and out of sight. You've already cut the floor pan in a bunch of places so fabbing a couple of muffler reliefs should be easy. You can dump the exhaust before the axle or take it up and over if the ladder bars have clearance in that area.