JEC, all I know is what I read in the manuals, and on websites, but I"ll pitch in anyway:
This site, and others, sell that same in-hose thermostat for the 8N and TO-20/30, among others. (I got one from this site for my TO-20, and it fit fine, and seems to work fine. I think the price may even be lower now than what I paid for mine.)
That said, the Parts Book for the TO-20 and TO-30 lists both a 160 degree version and a 180 degree version of the in-hose thermostat.
It"s my understanding that the TO-30 should use the 180-degree thermostat, with a 7-pound radiator cap, while the TO-20 uses the 160-degree version, and a 4-pound cap.
(On my TO-20, I"m using the 160-degree thermostat, and a new 4-pound cap from my local parts store.)
Hopefully, someone with more experience than me will weigh in.