Why not just swap oil pans? There must be a bunch of 235 pans out there that will bolt right on. I agree with the others that you've probably got some sort of heater for cold weather warm-up, but once you start welding on your pan, it will probably warp and leak. Maybe once the heater is removed, simple pipe plugs could be used to fill the holes. The pan will have to be removed and cleaned, no matter what you decide to do.
Jerry