Reddit reviews Kat's 13150 1500 Watt Aluminum Circulating Tank Heater

They make cab heaters. I have one like this in one of my classics.

I've never seen a head bolt heater that actually gets the engine warm enough to get the heater going more quickly when it's legitimately cold out. I prefer an engine preheater like this (installs between the rad hoses and circulates as it heats), or an auto start.