F M J bodies are prone to A arm failure if they lived in the rust belt and were not oil soaked annually. I say this because I'm from Ontario Canada, which is the salt centre of the world and this is the only car I've had suspension part structural failure from rust.
Here's the pretzeled A arm on my 89 5th Ave after it failed (and a pic of how the tire leaned into the car). This was after a normal 90 degree turn at around 10 mph. Rust had weakened the metal to the point that it failed. Upon closer inspection, the whole K frame was rotten. I therefore did a complete K member swap from a 5th in the wreckers in Oklahoma and have been good since (but my 5th no longer sees salt).
Some before and after pics and the pile of rusted K member I tossed included: