This thread details the steps needed to swap the guts of a real oil gauge into the oem one so you can have a working oem one. I did it to mine, it is delicate work.
As mentioned, all real ultra-lites use perimeter lighting so if you just put in the autometer one, the oem volt gauge next to it won't match. I put the boost gauge on my A-pillar so it is far enough away that most people don't notice. haha