Doug, just buy an electric (battery operated)
VEST. Motorcycle shops carry them. On the
really cold mornings (say, at 40* or below) these help a bunch. In fact, they can get too warm. Throw on some winter underwear (the thin variety you would use for skiing) and you'll be plenty warm from the waist down. I also use a face mask, the "bandit" style that covers from the nose down and attaches in the back with velcro. Easy to pull off a block before you arrive at your destination so that you don't look like a total wuss.
Get some thin leather gloves so that you can still feel the wheel, shifter and switches and that's enough to keep the hands from freezing over. I top it off with a thick wool cap. I look like a bank robber barreling down the 55 Freeway doing 80mph, but at least I'm warm.
Save your money and the pain of wiring something in your car and think portable.
-Dean