And to the contrary...
$900 may be too much for this particular V8 Z. What kind of condition is it in? If the motor is a tired oil burner/oil leaker, if the frame rails are bent/crushed/rusted through, body full of bondo, if the interior is shot, electrical hacked up, rearend whines, rust in the doors/rockers/floors/hatch area...
Did I mention that the turbo 350 is not a very desirable tranny for a V8 Z?
It may not be like this at all, but these are things you want to look for before you decide to drop a bunch of money into what seems to be a real deal.