I grew up familiar with "rubber baby buggy bumpers" too – in the Detroit area. However, the person I remember hearing it from was my dad – a New York City boy – so I don't truly know how well known it was/wasn't in SouthEastern Michigan, but I have a feeling it was...

As for stonker vs stonkered, I checked with my (English) hubby, who says that there's no "stonkered" over here, but "stonker" means huge – which could explain Ron Davies' suggested meaning (a guy could have a "stonker"), although hubby says he's not heard it used that way over here. He says its origins are military; a "stonk" was a brief, concentrated artillery attack. For example, a battery (4 guns) would suddenly fire 3 rounds each (for a total of a dozen shells), all at the same target, then stop.

I did some Googling, & found the wwftd dictionary, which has the following entries:

stonk
    a heavy concentration of military fire
    loosed a ~ on them and wiped them off the face of the earth
stonker
    [Austral] 1) to hit hard: knock unconcious
    2) to baffle completely: outwit, foil
stonking
    [Brit] 1) impressively large 2) an intensifier
    a ~ good time

Another word I found confusing when I moved here was "revise" – as in "Did you spend a lot of time revising for that exam?" (For the Brits amongst you, in the US we'd use "review" there; "revise" is used only in the sense of correcting something, or making minor changes.)