The frame details are very similar to my Eaton's Glider (Canadian department store brand made by Raleigh) of the same era, with one exception: on the glider the fender mount on the front dropout is set back quite far from the axle, while yours is very close (Is your front dropout made by mashing the end of the tube or is it a separate stamped piece welded in place?). Otherwise they could be twins!

I also remember the twinshift on bikes in my youth - I think we couldn't decide if we wanted to be riding motorcycles or driving cars in that era, so we did both (and still do to this day).

Mark