Did some trial fitting and came up with the solution for my '86 FJ60 project vehicle's exhaust system. I've got a lot of parts laying around, so decided to try out some ideas for which parts to use, routing, etc.
First I tried my new Man-A-Fre cat-back system, it's been stored in my garage for ~15 years now, never used. Started out looking like it might work OK with the OEM catalytic converter. It cleared the new OME suspension, but because of the oval muffler, the muffler was right up against the bleeder screw for the LSPV that was transferred over from my '89 FJ62 donor vehicle. Besides, I'd have to have a shop cut and weld the sections together.
Next I tried my relatively new OEM muffler and tailpipe assembly. It's been on the donor vehicle since 2008, but I'd only driven the vehicle about 7,000 miles since then. Of course it fits up nicely, because it shares the same two rear hangers (just behind the muffler and near the end of the tailpipe) as the FJ60 assembly. But the section of pipe ahead of the muffler is shorter than the FJ60 assembly, and the FJ62 has a 2-bolt flange whereas the FJ60 has a 3-bolt flange. I like the stout hanger assembly at the outlet of the FJ60 catalytic converter, so I determined I could use that if I had a muffler shop fabricate a 6" long straight transition section from the front of the FJ62 muffler to the FJ60 catalytic converter. One end would have a 2-bolt flange and the other end would have a 3-bolt flange. I've got OEM spares from other exhaust pipe sections that I would provide, the 3-bolt flange is from the section of pipe ahead of the FJ60 catalytic converter, and the 2-bolt flange is from the section of pipe ahead of the FJ62 muffler. I'd have the shop fabricate this section first, then I'd bolt everything up from the FJ60 catalytic converter rearward. Once the 3FE/H55f/split transfer case is installed, I'd trailer it back to the shop to have the section from the exhaust manifolds to the catalytic converter fabricated, using the downpipes, Y-pipe, and OEM oxygen sensors/bungs from the donor vehicle.
Here are a few photos to show my trial fit: