I have used 235 thermostat housings and water pumps (1954) on two 261 engines - one for longer than 45 years.
What year truck will your engine be in?
If you put it in an Advance-Design or earlier truck,
you should strongly consider using this water pump relocation adapter. With the adapter, you would use an older style water pump (later water pumps - any style- will not work). Use an older style water pump with a pulley diameter that matches your year, and a groove width that matches your year (generator groove and harmonic balancer groove widths).
You will not be risking cracking your 261's head, as long as the "848" head has been properly drilled for the extra coolant passages to match the 261 block.
