From:  http://forum.studebakerdriversclub.com/showthread.php?66058-Leaking-Heater-Control-Valve-in-81-Avanti   October 2012

I had my '81 out the other day only to see drops of anti freeze dripping on my mat as I pulled into the garage. What to do? Well as everyone has told me over the years when I inquire about parts for my '81 is " use whatever GM used in '81". I thought I'd start there anyway. After checking my sources at NAPA-all '81 valves were vacuum controlled & didn't look like mine. The short of it is I contacted vendors in Hemmings & found Joe Hudacek in WI. who rebuilt it to new! He IDed it as a '66/'67 B Body Mopar(Charger). My control valve is pt. # H 164458 Ranco.The Mopar # is 2607027 or Four Seasons #74665. Why would they have used such an old part # on an '81? Was Chrysler dumping that stuff? Well I hope my experience can help someone else out there.
Rob in PA.