What are we looking at there? A standard 45 fitting butted to the pipe at the floor and then a street L 45 going into it? I think I would cut a section out of the pipe above the fittings, cut through the middle of the street L and then try to separate the remains of the street L from the bottom 45 by cutting it into little sections with a dremel and prying out each piece. This still won't put you at floor level though and you're still going to have the problem of T'ing in at a point where you also need a 45.
Is the pipe above just venting or is it carrying waste down?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13