Looking for some help on old Chrysler flat heads. I have 1952 R12 Bombardier, 251 flat head, engine is stuck, spun a bearing I think. Think I have found a 218 out of a 1950 Dodge PU. This engine is whole, still in truck, supposedly ran a few years ago. Not sure I believe that but maybe. If it isn't stuck I'm fairly confident it will run but I think its about 15 hp less than 251. Not sure what kind of difference if any that would make? I'm also not sure if I can just bolt it in place or is there differences? I know the 218 is 23inch head and 251 is a 25 inch head. BTW Chrysler made flat heads into the late 60s, never knew that until I started researching this issue.