Snappy, thanks so much for the info. Just finished assembly with the new motor and as promised did not have to change holes in the radiator. I used a piece of scrap masonite so the motor would fit flat against its mount in the heater radiator, but other than that, the change out was simply nuts and bolts stuff! Hurray! The only remaining question is whether or not I can use the 6 volt resistor switch which gave it two speeds or if I need to get a 12 volt model of such a device. Do you know? Thought I'd give it a try at the risk of burning up the switch. What do you think?