"H" Valve for dual heater core

[Chatt69chgr]

I was surfing through the Year One catalog and ran across this:

http://www.yearone.com/serverfiles/fbshopmain2.asp?input=HC6670&SM=1&SC=

It's a repop "H" valve used in 66-70 B-bodies (part number HC6670) equipped with A/C and dual heater core.  It goes inside the heater box itself.  I have seen this valve in a couple of heater boxes I took out at the junkyard and thought that it would be nice to replace it when rebuilding my heater box in my 69 Charger as a matter of course.  But I never did see one for sale until, apparently, now.  It cost's $89.95.  Does anyone have any familiarity with this valve and does anyone know if Year One is the only place that has it?  Of is this something that never goes bad and is a waste of $$ to replace when rebuilding a a/c heater box? 

What I believe to be this valve is shown on page 24-9 of the FSM as Figure 5 and here it's called the water bypass valve.  There is a description of what the valve does in the FSM on pp 24-8 &24-9 under the paragraph REHEAT COOLING CONTROL.