Kevin -- take a look at Kims Hot Start small Thermosiphon heaters . They are inexpensive $125-150 apiece. Bob Lico recommended
them to me 6 years ago and work great. Keeps engine warm and dry. No engine sweating- no rust- no corrosion. Keeps engine block and oil warm. Been using them and are great.
I've used them with some success on my Ford 7.3 diesels. The pans rotted from snow salt after 15 years and I chose to install actual coolant heaters in freeze plug locations. The coolant heaters work much better......
The TPS heaters from Kims, are not produced by them. They just sell them.
Spent quite a bit of time on the phone with HotStart, who actually make these units.
Was an interesting conversation.
My question to those of you that have purchased these heaters, do the Thermatostaic heaters (TPS) work, as opposed to the ones that actually have a separate pump to circulate the coolant ?
Those are the EVR 20 series.