I have a 69 Chevelle, I plan on putting in 4 new heated seats (front and rear) when I start my interior. Do I need to upgrade my charging system? If I do, how do i do that?

We need more info....

What alternator/charging system do you have?

What is the current draw of the seats??--figure worst case scenario--all 4 seats ON/High working at the same time.

It's a 78amp internal voltage regulator alternator. I dont know the current draw of the seats because i didnt buy the heated seats yet.

Hmmm, 78 amp alternator might be cutting it pretty close...Figure it's winter time, you've got one or more seats on, the headlights, the heater on full blast...you get the idea. The factory A/C cars got a 61 or 63 amp alternator. I'd be very curious though, first off, to find out what each individual seat is rated at (amp wise) when it's turned on HI heat.