I bought an 87 Z24 (2.8 liter, 3sp automatic tranny)-- it was only 3 months old, only 8,000 km's on it in when I bought it -- so only paid $12.5K plus tax.
While I agree that the quality of various parts of the car were "less than to be desired" (IE my electronic dash burnt out in 3 times in the 13 years I had the vehicle, and the car did have a fair bit of rust around the wheel wells that started to develop after about 8 years..
I had great luck with the powertrain. In 2000, I sold it with 245,000 kms on it (for $100). It had original engine and transmission, and both were in great shape. ( I changed oil every 5,000 KM with standard oil, but, believe it or not, I never changed the tranny fluid once. At about 150,000 KM, a lube shop recommenced I change it due to it being dirty, but, then after talking to a few people, it was recommended to just leave it at that point -- which I did !)