84 c10 ls swap questions.

okay i believe i have it figured out but im not %100. i plan on pulling the engine, transmission, harness, and ecm, from one complete truck. im getting a lq4 or lq9 6.0, 4l80e and the harness with it as well as having vatts diabled. the mounting is simple. im using the ebay 1" setback plates and moving and modifying the transmission crosmember as needed.. for the harness im going with the stock harness modifyied as outlined on lt1swap so ill intially have 4 hook ups. 12v switched, 12v constant, ground wire, and the starter wire thats it. my question is, after i get that hooked up do i just discard the old engine wires that are not use? and i also believe i can buy the adapter to go on the transmission for my mechanical speedometer and my other sensors. i plan to go with a cable style throttle not electric so thats no issue. and how would i hook up shifting linkage/ will it bolt up to my column? am i missing anything?

Oh and also an 87 tank with a high pressure fuel pump of some kind

Or an inline pump? What would you reccomend? could i keep my dual tanks or no? It will eventually be put under some boost