So with the uptick in talk of problem with China and EMP potiental as well as the fact I live in ALaska and travel remote vibration prone gravel road I have been looking at getting a spare ECU just in case.  In trying to find info on them it gets confusing pretty fast to me. Some are described as "plug and Play" some state they need to be "programed" or "Flashed" and some are described as only needing the PROM card swapped to the new one.  Trying to find more details on the web seems to only add to the confusion. Does anyone have any experience/knowledge to share on the subject?
I realize that I should probably also have a throttle position sensor spare . Anything else I am missing?
Thank you ahead of time for any help anybody can offer!!!

Well I am going to give this build thread thing a try.  It  won't be uber exotic nor super expensive but might have a few unusual things.  There will be a little bit a flurry  in the beginning but slower after summer gets here. I live on a "homestead" that I have built from scratch and have many more projects to come. Our summers are short so truck projects will go by the wayside as I work on the property .
I have had Land Cruisers for many years with lots of fun with builds along the way. My last one was a '93 that had way too much electronics on it. When that got totaled in a wreck (kid pulled out in front of me) I decide to switch gears a little and went to a little older Suburban.  Some of the reasons were similar to Don's Square D build. I am a retired career paramedic/firefighter as well as outdoorsmen and have always been into being prepared and ready for whatever gets thrown at me. My goal is capable,reliable,comfortable and self-reliant. Similar to a expedition build.
So what I got is a 1990 Chevy Suburban 3/4 ton with  350 V-8,Turbo 400,NP 241. Remarkably free of rust ,just two very small spots. I know the TBI has a computer so I need to explore how to keep that going or get a spare. The engine is brand new and the previous owner was an aviation mechanic in the military. Everything on it is new except the AC. The tranny was rebuilt about year ago by a local shop with a good rep.

So my current thoughts are

12/24 volt system to run a ReadyWelder
Invertor to run hand tools
Roof rack
Possible find a way to add a PTO
Cargo drawers convertible to bed in back with 3rd battery for camping
Asst tools,recovery gear and some spare parts stored in it
Ham radio and possibly CB radio
It came with a 8274 but will switch it out for the 12k Warn form the Cruiser. Might put the 8274 on my tractor for logging.
Rear winch
On board shower
On board air of some sort    CO2 vs compressor
Custom by me front and rear bumpers with possible tire or fuel rack
Possible extended fuel tank.
Lift kit
Larger (with-in reason) tires
So there are the opening ideas. I have only had it a short time and still developing and looking at ideas. Here is a pic from the ad that I bought it from

Now we can see what I come up with or ideas you guys come up with that sound good! Always open to ideas.