I replaced the 6v blower motor in my '54 with a 12v motor from a '60 Impala. Most people use an aftermarket 12v motor from an auto supply house. Some have inserted the aftermarket motor inside their old 6v housing. If your 6v motor works and you decide to remove the guts from it to insert an after market 12v motor, PLEASE don't destroy yours -- instead ask other Stovebolters if they would trade their non-working motor for your working motor.
< click > to read the saga of my heater rehab and motor conversion. There are links in the post to Deve Krehbiel's heater rehab including how he inserted a 12v motor inside his 6v housing. Other links showing how DADS50 used a 12v motor inside his 6v housing. Plus a discussion of the types of 12v motors available to use as-is, without inserting inside a 6v housing.
I'm not sure if the resistor in your 6v heater fan switch can survive 12 volts. Brad Allen is the resident heater switch expert. He can tell you what to do. Try not to destroy your working 6v heater switch - they are pretty rare, too.
Do a search on Stovebolt for more info on your heater. There is a lot of good info.
Good luck.
