The Howell harness in the picture only works on 97 and older 4.3's. 1998 and up 4.3 are harder to install due to computer and wiring. On these models (98+)you can have the stock gm harness reworked and the computer reprogrammed to have the PassLock(security) system programmed out.  BTB in Nevada does a good job of this. The adapter stuff can be bought from Advance Adapters and they can send you a manual that has good info in it. There are too many variables to just have a tell all conversion write up. Downey offroad is also a good source for parts and info. I put the stock gm fuel pump in my Toy tank with major modifications to the tank. You can make the stock toyota tach work. The oil pressure guage and water temp guage can also be used by buying adapters to screw in the Toy sending units. The radiator from advance adapters works well. The gm fan will fit, but when rock crawling it does not cool enough if you do not have a fan shroud. I ended up using a flex fan and making my own adapter for the fan. I also made my own fan shroud. My install is on an 82 by the way.

If you have specific questions feel free to ask. Sorry I was an a$$ on my first post.