Here is a nice T/A. Almost 400 (AT THE WHEELS!) 14k pretty cheap
http://www.ls1tech.com/forums/showthread.php?t=500496
Good looking red T/A 35k miles 15k
http://www.ls1tech.com/forums/showthread.php?t=464494
My Thoughts...
1) No real difference between the SS/WS6 and the Z28/TA. Other than appearance, they both perform nearly the same.
2) LS1 5.7liter engines kick out some serious hp. When my car was pretty much stock; I went with a bunch of buddys who were in a Mustang club. I only had headers, catback, and an improved air induction lid. I dynoed at 342hp/353tq at the wheels while alot of the Mustangs GTs and Mach1s with comparable mods put down anywhere from 250-315ishhp at the rear wheels. Forget all of the rated horse magazine bs, these are real numbers to the road, not flywheel hp #s.
3) Cheap to fix, cheap to modify (errr cheaper than other cars to modify). I put down about 2grand in mods, lid, exhaust,intake, stall converter, and was running low 12s (with a 1.6 60' time) with better tires possibly better (maybe 11s possible). No small feat with no internal motors touched, i.e. a cam (easy swap), or heads (a difficult swap). Oh yeah, i weigh alot b/c its convertible.
4) Should you decide to go with a Camaro or TA. I suggest an automatic if you like dragracing. They generally do better for comparable mods. Beware tho, you need a stall converter if you wanna do any random street racing, 20-25mph is the deadspot for the autos. But if you are the man jamming the gears, get a manual.
If you want a solid cheap platform, go with the LS1 F-Body line (99-02). It has THE EXACT same engine as Corvette (non Z06), the only reason vettes tend to do better is b/c it weighs less.
As with all cars, it depends on how the car was treated, its condition, and how you do your maintenance. Oh btw, the only mustangs I ever had a problem with were the 03+ Cobras (a 20k+ car), thankfully some of the owners cant drive. Its nice to know I spent about 14k on a nice car that I can put sideways at 40mph.