Hi and welcome to mightyram. You are on game with your plans. Never ceases to amaze my why anyone needs to butcher the simplest wiring in the universe to make it work but it happens all the time. Both window mechs are available new in pairs - https://www.ebay.com/itm/FITS-MITSUB...AAAOSwgsxaa5YF
Don't know what the quality is like but it has to be better than the 35 year old winders. No doubt you've already investigated what goes into a twin cam build but there are a couple of sources the 4G63 can be picked out of (early Hyundais and Kias besides Mitsubishi) Your truck looks nice and straight. A good intro. Keep us posted with progress and ask Q's when you need to