Wrong time of the yesr to get the heater working, but I agree it's worth it. On a Mid winter day racing a car at Goulburn, we were able to put the heater to recirculate, which kept the car interior nice & warm & all the windows clear on a very wet day. This was in a stripped out Sunny coupe with an L18, & was a victory as my co-owner had given me real grief about wanting to keep the heater in. Very easy to do, as well. Just a straight piece of heater hose from the side of the head to the heater valve & turn the outlet hose so I could run it across the back of the head & down the side of the engine to the fitting. Looks factory, even.
For a genuine heater valve, try abouttime spares on http://www.abouttimespares.com.au . I got one for a 120Y a few years back.