I doubt they are compatible. The 97 TC likely has the older style rear suspension which has a single control arm on each side and no watts linkage whereas the 2000 GMQ has an upper and lower control arm on each side and watts linkage. You'd have to check other mounting points for the coils/air bags and other components.
It's unfortunate if you are unable to use it, but as one of the Town Car service drivers in the respective forum is concerned, using aftermarket MOOG variable rate springs is a good alternative. I can't comment on this.