Any of the G-body could be had with a diesel. Olds might be the best bet to find one with a diesel. The B-bodies are the fullsize GM's, like the Impala, Caprice, big Caddy's... I think you will run into the housing to be too wide to get a wheel in the wheel well of a g-body. You would still run into the changing the spring perches and everything else.
Out of curiosity, what are you plans for the car? I'm puttin' 400 lb/ft through a stock axled 3.08 geared 7.5" with a locker, and still haven't broke anything on a set of sticky drag radials.