I don't know how much you'll be able to find on it -- especially if it's not been titled in a long time -- but your DMV may be able to give you a history for a nominal fee, and there's always CarFax (or whatever it's called).
Keep in mind that in 1946 they didn't have computers in DMVs, and by the time that they had a large-scale, centralized network (1990's), they probably didn't enter any more of the old data in than they had to.
As for what number to go by... Use whatever's on your title.
