My Demon came with a non- original 225 with non-original matching auto trans on the column. There is no trim tag (it rusted out). So my question is, without a trim tag or build sheet, is there a way to tell if the original engine was a 198 or a 225 slant six?
Did you look for a build sheet? They are often found in the seat springs, behind the glovebox, under the flooring, and other places. That might have a clue for you.