I wouldn't replace it. I got my replacement from IPD a couple
years ago; it is a part for any 140 years 1966->72 but I think
a later part can be made to work.

But, as I said, I wouldn't replace it. I would instead use an
inline valve from a water-cooled VW (rabbit/golf/etc). These
parts are small, have a place for mounting a cable, and can
likely be put entirely in the engine compartment just by tapping
into the heater hose.

The stock unit is silly -- there is no reason for the automatic
opening and closing feature and it often winds up failing in
either full blast mode or "even when it's off it's on a little"
mode. Mine, only 2 years old, at part heat settings, makes an
annoying buzzing noise so I either have it all off or all on.
chris