stock internals are good into the 10's, and someone just went 8's on a stock block. upgrade the fuel pump and you are good into the 10's at least.
Oil leaks are the biggest known problem, and that is just because they are getting to be so old. the stock head gaskets are REALLY strong.
Just remember you are buying a car that was made 20 years ago, and make sure to get an 86 or an 87. Tranny will only go 12's and then you will need to have it built. Oh yea, and tuning the cars sucks, it is all mostly mail order, but it is normally pretty close.
http://www.turbobuick.com
http://www.turbobuicks.com
http://www.t6p.com
http://gnttype.org