I have a couple of those "puzzle boxes" for my 27/28 treadles, plus a bunch of loose attachments. It took a lot of work to complete the boxes and every time I see a complete one on eBay, I still want to buy it. :)
Modern low-shank feet work just fine, so my 27 had a Lucite 1/4" foot and a nylon/metal darning foot mixed in with her collection of era-appropriate feet. :)