Not possible I'm afraid. This is defined in the MDL file. Most 3rd party aircraft for CFS1 will have some sort of internal views (virtual cockpit) but the DVC with fully functional gauges was not practical until CFS2 was released.

You might need to tweak the viewpoint in the AIR file. I've found that many are set up wrong on earlier FS98/CFS1 designs. This can be edited with AirEd from the Aircraft Design section.