This project is possible, and can be a ton easier than whacking off the roof. I was driving 145's then 245's and sunroofs were never an option. I was kicking around the idea of a SR install in the 245 wagon, so my friend and I headed to the U-Pull for some research. We discovered the following by popping out the one piece headliner in a 4-door 244 w/ factory SR:
* entire SR unit is mounted in a "tub" that is glued to the underside of roof.
* Tub has a slight curve as sedan also has it--wagon roof is straight. We bolted a brace to L & Rt.rear sides of tub , w/ flat bar stock, bolted to roof supports above rear doors. Your 242 should have the same curvature as any 240 sedan and a 2/4 door SR tub would be the same. You can pop the seam sealer loose between tub and roof. We used a manual "crank" style roof opening.
* The CUT. You only need to cut/remove the SR opening, taking a flange/lip of about 4 inches around the hole in roof of donor car. When you cut this square flange, then pop the tub loose, you have the whole kit to install. You do not want to just cut a hole, unless you are a master body pro. We measured the SR car from opening side to side, from the slight edge where flat roof tapers to drip rail and from windshield taper---did all this until we had it figured out, then did the same on my car. Much credit to my Fellow VoVo enthusiast and master mechanic, because cut matched flange on SR perfect--no gaps!! Then propped tub to floor w/2x4 pc's and welded the SR flange. Check Headliner fit.
* Go see one at junk yard. You need a committed/skilled friend. Regards,Ken