The "2 converter" systems on the first gen Explorers isn't really 2 converters, it's one converter split into 2 housings, the first one doing the reducing, the second one doing the oxidation.
I would say for emissions performance, it might be preferable to replace it with the same thing, since the reducer is very close to the Y-pipe connection and would heat up the catalyst faster. However, direct-fit replacement converters are over $200, whether you get them from Walker, Magnaflow, or even lesser known companies. The benefit to these is you can turn some bolts (or break off some rusted ones and get new bolts) and replace it yourself.
You CAN throw on a universal 3-way high-flow converter (mounted where the 2nd housing is in the stock system), and just take up the rest of the space with 2.5" or 2.25" pipe, but the fab work on the Y-pipe end where the tube is ovalized usually leads to an expensive pipe just the same. Some shops will just take a tube and stretch the end to fit, which is ok, but you wind up with a very thin section of pipe if a 2.25 pipe is stretched to fit this connection. I'd prefer to have two pipes cut and welded to a third center pipe to make a clean, stretch-free oval tube. You also might want to have the same kind of gasket end at the muffler pipe as OEM, since it allows the heavy muffler and exhaust to flex on the rear rubber mounts.
I wouldn't move the converter back any farther than where the stock 2nd housing is, otherwise it might never get hot enough to do it's job properly, and you might wind up with a poor flowing system.
If you don't have one already, I'd suggest getting a cat-back exhaust while you're replacing the converter. A Dynomax Super Turbo is great, and they make a complete cat-back system with mandrel-bent pipe. I'd suggest getting the system for the 91-92 and changing the muffler hanger on the '94 to the 91-92 style. This lets you use the muffler that's 2.25" front and rear for better flow. The 93-94 systems use a dinky 2" pipe between the converter and muffler, and also have the muffler hang down lower due to the single rear mount.
