A quick test
I had an OEM 87 C unit handy following resolving my 16502 / 16512 errors, and before returning it to the dealer gave it a quick hot water test. It appeared to begin opening in the upper 180s, which approximates 87 C. At boiling it had an opening of 1/4" or so
I wasn't sure what the temperature rating of a t-stat meant - whether it begins opening at the labeled temp or is fully open. By this test it appears to be the beginning of opening.
Awhile back I replaced the stat in my powerstroke with a 203 F unit. I don't recall what it had before, possibly a 190. That truck has an aftermarket digital temp guage and its typical operating temp went from 177 to 191. The digital guage clearly indicates that the stat sticks a bit before first opening, allowing a temp of 199-201 before opening, at which point the temp drops to 190-191 in a matter of seconds. I think I picked up 0.5 mpg on a truck which yields low 20s, but we all know the futility of assigning mpg changes to particular events, owing to all the variables.
If I find the Stant 195, I'll try it in the saucepan before installing it.
There is a 205 Stant unit, p/n 13352 which has the same 2.125" flange diameter which implies it could be installed, but it lacks the secondary springloaded bottom flange, so I'm unsure what the consequences of that would be.