I never heard of a 250 before, but a transmission rebuilding catalog I have at home (I'm at work now, don't tell anyone) shows that 13 bolt pan as a 350 or 250. It is in a 82 malibu with a 229 v6. What is the difference between a 350 and a 350c? Car will probably get a bbc and t400, but I'm curious about the existing trans.