I just upgraded my Model B. Purchased the PM-5 for it, along with the newer rollers for the front feet. The PM-1 still works just fine, but one of the 2 mounting tabs for the cage is busted (came to me in this shape when I bought it off eBay many years ago). It will still mount and hold onto the cage just fine with the one tab. Also have an old set of rollers for the front feet; these are an older version that go under the front feet and are held on with a single bolt. They are dirty, but still work fine; I just liked the looks of the new upgrades.
Anyone in the Lower 48 of the USA that is interested in these is welcome to them for the cost of the ride to your place.
Joe