IMO a GT will pull a bit more than a similar GT/CS...
As a C code, $17-22 seems a bit high, unless its perfect (e.g. investing far more, even doing a lot of the work yourself), saw a few a year or so ago in the 12-16 range in very good condition, can't believe the market is going up under current economic conditions... ???
GT/CS fiberglass and taillights 1.5-2k
paint 2k, supplies alone (consumables - paint, bondo, sandpaper, primer, etc)
engine repairs/rebuild 1-5k
trans $500-1k
rar end - ? new center or ??
rims/tires $500-1k
suspension - 500-1k
interior 1-2k
chrome 2-3k
all the other "little" things 2-5k (brake lines, fuel lines, wiring, glass...amazing how fast it adds up, can go 500-1000 in AMK bolts alone if you go that route)
labor, unless you do "it all" what...$40-70;hr depending on location x a minimum 4 weeks = 160hrs x 40/70= 6-10k...
The the rust.... $$$$$ or a ton of time to DIY sheet metal, maybe 1k for the extent you mention (full floor is $500-ish) (I can't do it so a big cost to me)
It adds up fast and will likely go over 17-22 without even trying...