I found a few used ECMs on ebay and ultimately bought one from a vendor called 'partwheeler' based out of Colorado. I chose them because of price, they didn't require a core, and look to have a pretty good return policy if need be.

I placed my order this past Wed and was told I would get it either Mon or Tues next week..........it arrived today (Fri).

So, right after work, I went over and installed this 'new' ECM.................. The truck fired right up. The truck is still on stands, so I just let it idle for about 10 minutes or so. Even without driving it, I noticed two differences almost immediately, the OD switch works properly again, and the tachometer works again. Hard to tell 100% without driving it but throttle response seemed quicker too when I winged it a few times.

I'll go over tomorrow and put the bed and wheels back on it so I can give it a proper test drive.

While looking for ECM's on ebay, I came across a vendor that rebuilds/refurbishes ECMs (all models) I may go that route with my original one to have it as backup.

Big THANK YOU for all the help with this problem! It is VERY appreciated!