Both 160 and 180 are listed in the shop manual (page 6-88) as being acceptable for use with permanent anti-freeze:

A 160 will begin to open at 157-165 and fully open at 185.

A 180 will begin to open at 175-184 and be fully open at 204.

I've never had mine off so I don't know if its stamped 160 or 180. The engine runs at 180-185 year round. A 180 T-stat will never fully open if your engine typically operates at 180 degrees, however.

I'd take a look at your old T-stat and see what temp is stamped on it and install the same one.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)