Just in case anyone wants to make a puller, it can be done. The prechambers in my 74 240D were really stuck (maybe they always are), and I didn't feel like getting the expensive tools, so I made my own.
This is what I did: I had an old, broken prechamber lying around, so I used it as a die to make threads on a piece of 1/2" brass plumbing pipe. It turns out that that 1/2" plumbing pipe is exactly the right size for these threads, and it is hollow, so you can put a bolt through it. To make the threads, I used my little Sherline milling machine to make vertical slots through the internal threads on the prechamber. This can easily be done with a Dremel tool, but you have to make the cutting edges sharp, and cut out as much of the threads as you can. Ideally, you would have about 6 or 8 cutting edges about 1/8"-3/16" wide with all the threads in between removed. Then file the end of the pipe so that you can get it started to thread and use a pipe wrench to turn it. I used another old head to hold the prechamber, but you can find a piece of pipe or an old socket that fits around it and cut a slot for the little protruding tab. 3/8"-1/2" of thread seems to be enough. I found that a 3/8" carriage bolt head would just fit inside the prechamber threads, so that is what you use to pull with. The angle of the prechamber hole and the lack of a regular surface makes pulling somewhat difficult after the prechamber is raised up a ways, but until then, you can use a socket on top of the grooved nut to pull against. Afterwards I used soft plastic and wooden wedges with a steel plate on top.
An alternative to cutting the threads yourself is simply to have a machine shop do it, as they can set their lathes to cut practically any combination of pitch and size. Test the thread pitch against several smaller metric bolts to see what it is.
I hope this can be helpful to someone.