Thanks for the replies. I decided to bypass the coolant flow to the servo by (1) using a reducer to connect the 1/4" hose from the aux water pump and the 5/8" heater hose (2) a 5/8" nipple to connect the other, two, 5/8" hoses that enter and exit the servo nearest the firewall.

Since I left the vacuum lines and electrical connections on the servo, switching from defrost to bi-level slows the blower motor down, but doesn't allow me to control the temperature. However, I can live with that, at least until I decide whether to get a used or rebuilt servo.

I considered getting the digital version, but I can't justify paying an exorbitant price for a system that costs less than, and probably a lot less than, $100 to make, even considering start-up costs.