I discovered this about 5 years ago when I was getting into wheelwriters, that the wheelwriter spacebar and "code" key would fit on a model M. It requires you to move some spring around thouh.
A few years after that I decided to mod one of my terminal model Ms to be bolt modded. I think I was bolt modding all my model Ms I swapped some things around but I couldn't get the "-" key on the numberpad to work. I now suspect I was just using the wrong key in soarer's firmware but oh well. I ended up cutting the traces off the PCB.
I wanted to use a terminal M because you need a controller / converter anyway, and I needed it so that I could remap the keys. I also like how the controller bolts to the back of the plate instead of just sitting in the case. Finally, I liked the cable channel on the bottom. I actually did a lot of work trying to get this working, I grabbed a new controller, another compatible terminal controller, a new membrane sheet, etc.
So today I grabbed a teensy from my order and soldered it up. What remains is to grab a USB cable and to program it. I might cut the USB connector off the teensy to get it to fit better: still not decided. Here are some pictures. As always, ask questions and I'll answer them next time I'm online.
P1090869 by
dork_vader_exe, on Flickr
P1090870 by
dork_vader_exe, on Flickr
P1090871 by
dork_vader_exe, on Flickr
P1090872 by
dork_vader_exe, on Flickr