Kevin,
There are a few components to look at on your exisiting system that could make it nonfunctional. The engine compartment blower needs to be working to allow the inside footwell blowers to operate. This is the most common failure so it might be something to look at. Lots of info here:
http://forums.pelicanparts.com/porsche-911-technical-forum/258473-help-does-anyone-understand-footwell-blower-circuit.html
I backdated the heating system on my 78SC with SSI heat exchangers,removal of the rear blower and installed footwell blowers. I have tons of heat now. Here is the thread:
http://forums.pelicanparts.com/porsche-911-technical-forum/320814-how-install-footwell-blowers-pre-84-911s.html
There is info on changing the handle brake lever to one with the red heat levers on either side of the hand brake that might be useful to you.
If your footwell blowers are working you could modify your system to function the way mine does.
__________________
Peace, Ron
www.ronorlando.net
78SC Targa 3.2 SS, 964 cams, CIS, SSI's,Dansk
Own a gun and you can rob a bank , own a bank and you can rob the world.