I'm using Ed Klepeis' heater core.  He makes a really nice unit that includes the core and fan.  You just need to make an air box and direct the outlet to a scat tube.  I also installed a water contrtol valve that I got from Summit Racing.  I actuate the shut-off valve with a non-mac servo (http://www.servocity.com/html/servos___accessories.html) and a servo-controller from Eric Jones (http://www.periheliondesign.com/moreproducts.htm - scroll to bottom of page).  I also put in a flapper (Aircraft Spruce) on the hot air output that will change the direction of the hot air from my feet to a defrost outlet in my glareshield.  This is also controlled with one of Eric Jones' controllers and a servo.  

So, my heater electrical system consists of a fan switch (provided by Ed Klepeis), and two servo controllers.  I don't have any pictures, but if it would help, I can take some.