Ive basically done everything to my clean pepsi 126710 gmt to make it look like a gen Rolex GMT-Master II White Gold Meteorite Dial 126719 even went as far and had a very nice custom meteorite dial made which matches the rolex gen version pretty damn accurately, and full gen 116710ln bezel assembly, click spring, retaining ring, crystal gasket, crystal, hytrel ring, crown guard etc. my question is whats the best way to make it white gold now? Have someone plate it? Someone suggested white gold heat treatment, which I’m not sure exactly what that is?
Don't do the heat. It's a stupid suggestion.
Rolex White Gold isn't plated with rhodium so rhodium plating the watch doesn't make sense either. They use an expensive process of literally pouring palladium and rhodium into molten gold to create solid White Gold. It will never turn YG like traditional WG jewelry does.
There is other options like Stullers x1 white Gold. It would be closer to Rolex WG since it doesn't need rhodium plating due to its crazy white alloy appearance.
If you decide to plate it with just rhodium then it's gonna look chrome like. Rhodium reflects back like 80% of light.
It's a long boring process because you have to polish the watch so the surface blemishes don't show up.... Plating won't conceal them..... Now you gotta activate the metal to adhere to the watch surface. So then acid gold strike to cover the watch in metal to get the adhesion. Then add bright nickel of 15 microns before the final rhodium flash. Nickel also gives corrosion protection.
If the rhodium is too thin then surface tarnish will form quick because rhodium is porous.
This won't last long since it's a watch and takes a beating when we wear it so expect yearly replating if it's an everyday watch.
My opinion would be to keep it SS and say it's a custom build.