Great reply and it is very much so appreciated. Your name was mentioned as someone to talk to.

Here's the interpretation I have as of now as to what I am going for:
~Convert the LS harness to standalone as if the engine/tranny were going into any older carb vehicle. The 5.3 harness controls all engine and trans functions.

~Remove only the engine control portions of the 4.3 harness, basically remove the parts that are left on the 5.3 harness once it is standalone.

Old harness goes to:
- alternator for volt guage.
- temp sensor installed in passenger head for guage. 5.3 harness uses the one on the front of the driver's head
- starter
- oil pressure location that you said to tap into oil filter bypass
- a/c compressor

I don't understand where the speedo and tach get their signal, or what changes have to be made going into the cab. I am almost getting discouraged at this point, lol. I know I can do this, but it isn't my truck and I just don't want to get too far in and realize I'm stuck. I've never been "intimidated" by a project before this one, but i've never not been unable to figure out and finish a project either.

I think my plan for now is to pull the 4.3 engine and harness and just start mapping things out. I have the workspace and I have the time with the truck, I just wish there was a little more easily laid out info on what exactly to do.

Again, thanks for your post and anything I got wrong or left out up there(I know there's alot missing) please let me know.

Electric fans are on the back burner, and I can easily install some standalone if I want them later I've done that before with just a temp controlled switch and a few feet of wire.