Tiny_Jaime,
The original 1962 (and other years) 261 thermostat was different from the 235 thermostat.
Different in brand/make (Dole) and a little different in operation, and maybe different in size (I think - maybe - see below).
However, any modern thermostat can be used, as long as it fits the thermostat housing you want to use. The 1960 thermostats started to open at around 160 and were probably completely open at 175-180 degrees.
I cannot find part numbers from 1962, but here are 1960 part numbers:
Harrison Poppet Valve (used on 235s, and V8s): T180
Dole Pellet Bypass (used on 261, and maybe V8s): DV50
Some sources show the T180 as a replacement for the DV50 (indicating that they are the same size)?
