Yes my solenoid will fit the IBM, though you’ll have to secure it in the case yourself. I recommend securing it well – feel free to experiment!
The screws are probably 6-32 inside. Just make an order note to add a 6-32 0.25″ length screw and I’ll try to include one for free with your order!
If you want to upgrade to USB-C I recommend purchasing my new USB-C xwhatsit controller which is based on the latest xwhatsit revision. The first group buy you purchased from used an older micro USB design. Otherwise it is likely compatible.
Also you will need to order the solenoid driver and solenoid itself.
All three items can be purchased here: https://www.modelfkeyboards.com/product/xwhatsit-beam-spring-or-model-f-controller/
See the above page for important safety and installation instructions.
Right now the controllers are discounted because I have just made a new batch of them at the PCB factory.