I found the "dual action" thermostat housing from one of the members here. I picked up the bypass thermostat that fits at a local parts store. As 4onthefloor said earlier, your best bet would be an old 2-ton truck or a school bus.

1962 Fleetside 4spd 235 w/O.D. posi 3:90
In the Stovebolt Gallery
1990 Subaru Legacy Wagon AWD 2.2 5sp
2013 Ram Tradesman C/V
My Webshot Photos]