Just a quick aside that doesn't help with the 1920's torpedo end canoes - in the 1960s, one of the Otca forms was modified to build 17' Molitor models.
As Benson says, it is a fairly trivial process to put different stems on a canoe to change the profile. Some companies molds (e.g. Kennebec) stopped a foot or so short of the stems, which certainly would facilitate this, even if it weren't done on purpose...