Well, I'm pretty well versed in my Transformers mythos, but I can't say I know everything as I haven't even watched all of G1.

Anyways, I've seen a "White Optimus Prime" and a Black Optimus Prime". I need complete historys of these guys and who they are. I've heard rumors that the White one was actually Ultra Magnus. I don't see this really though....

Also, links to the possible Action Figures/Models would be appreciated.

tl;dr: help?

The Black Optimus is called "Scourge" or "Nemesis Prime". The White Optimus is, more often than not, Ultra Magnus.

There is no way to give you complete histories on these guys because these characters exist throughout many different Transformers lines/continuities, many without media to define them as characters beyond what their action figure packaging may say. However, you might find some good info to use here:

http://transformers.wikia.com/wiki/Nemesis_Prime

and

http://transformers.wikia.com/wiki/Ultra_Magnus

Hey, thanks a lot!
I must have that White Ultra Magnus. I absolutely love it. Would you have a link as to where I can obtain it?

Happy to help, but could you be more specific? There's a couple of Ultra Magni on that page.

Uhh, the White one. Where he looks almost exactly like Optimus Prime.

Masterpiece MP-01 Prime was repainted into Masterpiece MP-02 Ultra Magnus

Classics Prime was repainted into Classics Ultra Magnus

Revoltech Prime was repainted into Revoltech Magnus

Ti WW Prime was repainted into Ti WW Magnus

You can see where being vague here causes confusion. There's a few of him "Where he looks almost exactly like Optimus Prime"

I see...
Well, I've long since found my answer. It was the MP-02 Magnus, btw. I should of said that I was refering to the Dreamwave stuffs.