[Clint]

Got it done today. 5-hrs start to finish inc lunch and breaks. Exhaust work is never fun. Simple work but tedious... cramped quarters, tight access, rusted bolts, gravel driveway (plywood helped).

Reset the ECU via "The Easy Method" described here: http://www.clubfrontier.org/forums/f8/need-reset-ecu-79125/#post1094191
Seemed to work (SES light went off). Then disconnected battery and touched cables for 30 seconds.
O2 sensor wire harness clips are a PITA (like most electrical clips on all vehicles) but eventually got them apart.

Not a chance removing bolts on each end of secondary cats; far too caked/rusted/seized (cleaned with chisel & wire brush, PB blastered, applied heat... snapped the first one... pretty much a waste of time). Switched methods: cut pipes with angle grinder; was quick and easy.
Manifold heat shields each had only 1 remaining bolt o begin with. Driver's side bolt snapped off easily and was then able to maneuver shield far enough up out of the way. Couldn't access remaining passenger side bolt (lower bolt) & didn't want to waste more time as it surely would have snapped anyway, so I cut a 2" chunk off the tail end of the shield with the angle grinder which allowed just enough access for the nuts.
The 3 manifold-to-cat flange nuts on each side were surprisingly not rusted at all and very easy to undo (except for the painfully tight access... ratcheting flat wrench was the ticket).
Install was much easier and about 1/2 the time of removal. Installed the O2 sensors prior to putting the cats in (definitely easier this way). Reused OEM flare nuts at manifold-cat junction. New 1/2" bolts for both ends of secondary cats.

Parts used are seen in attached diagram. 4 cats, "front pipe", and gaskets. All fit great. Old cats were not clogged up with any debris at all. O2 sensors were overdue. Truck seems to have original power resorted (only noticeable when climbing hills). Sound and volume are the same as factory as far as I can tell.
Will upload some pics of the old cats tomorrow & the newly installed system later this week.

What was the total cost for parts?