Thanks for feedback, y'all! OK, will put new leaf springs on the list - after 70yrs, they deserve to be replaced i am sure.

Finally found this most helpful YouTube vid about rebuilding Harrison heaters (of this model), and an exact-fit 12V Dayton motor, available from Grainger: https://www.youtube.com/watch?v=ADbPnCqJqbQ

So i will try that route, hoping it will put out more heat w/ replacement motor...this is cold country!