So I managed to find some beamspring keyboards at an electronics surplus warehouse:

I believe both of these are 3278's, though one of them did have a copy of the 3279 manual in the bottom compartment:

Although I haven't opened them up completely yet to confirm, I am guessing these won't have too much rust since the person who stored them put this weird plastic wrap between the switches and keycaps, but some of the stems got a bit bent due to the way they were stored (as you can see in the picture on the number row).
Anyway looks like I'll now need to buy some xwhatsit controllers from orihalcon to test these guys out. I'll need to remove all the caps to get rid of the plastic, so are there any things I should be aware of when attempting to remove the stabilized keys in particular?