I am trying to do this conversion myself also, is it possible to use a relay without a diode and add a diode later ? Looks pretty easy. If so what 2 posts would it go between ?
This could make the relays under $10 apiece
http://www.grainger.com/Grainger/Relay-5ZMU4 With
http://www.radioshack.com/product/index.jsp?productId=2036268&CA_6C15C=107608655&utm_source=BZ&utm_campaign=product&utm_medium=CSE
Thanks Rick