JW,
Not answering your question directly at first, but I love the heated seats and steering wheel in my modern vehicle.
An almost direct answer to your question, I have installed seat heaters that I'm sure are virtually identical to what you're speaking of in a 99 Taurus, 97 Saturn and an older Ford camper. All worked well and installed as you would expect. If you're already doing the upholstery, adding the heaters to the seat is almost effortless.
