I own a 1991 240 wagon (2nd owner) and enjoy doing the bulk of repairs and modifications
myself. I do not own any maint manuals. I have had the switch panel off a few times
(panel just to the right of the drivers legs) and finally noticed that the two machine
bolts which are to hold the top of the panel on securely, are missing. Would anyone
have any idea what size those two bolts would be?? They are recessed deeply into
the panel. Any help would be appreciated.

On another topic. One of the two halogen bulbs illuminating the dash
panel (speedometer) had blown out. Instead of replacing with halogen,
I decided to go with the LED bulbs sold by superbrightleds.com. I bought
two of their B10d high power instrument panel led's and a perfect fit with
excellent lighting. Led's are polarized, so after installing one in backwards,
reversed install and they both give some great lighting. Good for 20k hours.
Very content. You might want to go this route next time. And yes, they are
voltage variable, so the dimmer is effective.