The 3.8 Buick mill is much more reliable than the 4.3 by what I would consider a looooong shot.
It's been around since the 70's. It also responds to modification from your wallet to a lesser extent. 11's are easily attainable. If I has a Sy/Ty I would keep it stock and drive it every day. The Buick would be my weapon of choice.
^^^ x1000 i have had many of each and stock syty's are the only way ill drive them any more. they break too easy.
gn's when done right go fast and dont break other then a head gasket or two. or go cometics and dont worry about gaskets at all.