I'll do a full write up on this one day soon, for you detail fiends out there. I took pics during the project.
The writeup is here
ZeroStart circulating type heater #330-8001.
Outside temp this morning was 31 deg F. Engine was approx 75 deg F before starting it up! I got 54.81 mpg on my 55 mile trip to work, better than I've seen since early October and nearly as good as late summer.
Finding a heater that would work in my '97 (Gen 6) Civic was not easy. However this one does work. More details one day soon, either in the DIY forum or EcoModding Central.