Your trouble with getting shallow DOF are over. fleabay has some lensboards that are made for Plaubel 4X5, so you might try to visualize what will fit from the pics and what the front standard of your camera looks like. Also, S.K. grimes (APUG sponsor, I think) could probably whip one right up for you. There was once a page that gave interchangeability of lensboards, but I can't find it now. Anybody know where it went?
Oh yes, multiply or divide by 3 to get equivalent focal lengths between 4X5 and 35mm. It has some other aspects for LF photography, but that's the simple answer.