From the pictures on MUD it looked like the "walker pipe" blocked the oil filter? I used a flowMaster y-pipe when we built the exhaust on my 60. We stacked them vertically and then sent the single tube to a muffler and I dump straight down towards the ground directly behind the rear axle. I did have a little more room with a 60 as the frame rails are what 3" further apart?
My only mistake was giving the oil pan too much clearance and I had to drop my bump stops and inch to keep my front diff from contacting the cross over.
And as Tim said going back passenger side is not possible above and between the frame rails from memory. Either cross under the oil pan or go outside the frame rails.
Speski OffRoad LTD, Cargo Solutions for Toyota 4x4's http://www.SpeskiOffRoad.com
"80 series, with a fridge"
1976 FJ40, Project with little progress.
2004 Starcraft 10RT