I made an exhaust system for my '86 Ram W150 when I was working at an exhaust shop. 2" flared to connect the the mainfold, then I welded 2-1/4" onto the 2" right after the flange area. The pipes basically came down a bit farther before bending towards the back so there was plenty of clearance around the oil filter. Both sides came back past the transfer case, then the drivers side crossed over to the passenger side and ran both 2-1/4" pipes into a dual inlet single 3" outlet Imco chambered muffler (I think installed backwards), with a 3" outlet that went over the rear axle and exited out the passenger side at about a 45 degree angle right before the end of the truck. The end of the pipe was cut parallel the the bed side so it had the angled looking exit. It sounded pretty good on a mild 318.