I just called them yesterday as i have a 69, and the springs are molded into the pad. Nobody seems to make those anymore , so i have to order the spring assembly for a 68 deluxe. extra 90 bucks a seat. but without the springs , the cushins are useless.
I have bought seat pads with the integral wires in the backrest pad for my 1969 Firebird. I haven't installed them yet, so I don't know how the fit is. I bought them just recently from Classic Industries, part #SF109 (for DeLuxe interior). If you have a standard interior the part # is SF117.