I have a 328k. I've been using it a lot, since I found this board and was complaining about my Babylock machine being in the shop and someone commented that I should buy an old vintage machine for a backup. I remembered that I had 2 vintage machines in my basement that I mistakenly thought were old and useless. I read here how to clean up old machines and to my surprise they both ran just fine after cleaning and oiling them and now I use them more than my newer machine. The stitches just seem much more secure on the older machines. I only had the zigzag cam but I found some others on Ebay along with an original manual.
If the funky foot you have came with the machine it should say on it somewhere what it's for. I have a bunch and they all say "Singer" and "Hemmer" or "Ruffle" on the foot itself.