The thermostat or the housing is hard to find ?
Both, if you are referring to the 261 special thermostat. It is a non-standard-design thermostat (no one has posted a source of a replacement - a while back, someone posted a name for the special design) and I think it goes in a special housing (that will allow for the larger thermostat-height).
Regular 235 thermostat housings will work on a 261 but I think that they will not allow an original thermostat to fit inside. An original 261 housing will, I think, allow a normal 235 thermostat inside.
Also, the thermostat housing (and water pump) that came on one of my 261s (1960 from a large school bus) have an extra hose connector on the thermostat housing and on the water pump. I guess that they might have been used with a rear heater in the bus?
