The 604 is a 1982 model. I stopped by this evening, but couldn't get the hood open by myself because it didn't want to pop up on its own when I pulled the hood release. It was too dark out to get good pictures of the wheel wells of the car, but I was able to get a decent look at it and could not see any rust. Known issues with this car: driver's door doesn't want to open, the linkage is messed up somehow, brakes are quite draggy at the moment, battery is totally dead, even with a charge it didn't want to turn the starter or run the power windows. Yes, it is a 5 speed.
As to the 505, to the best of my knowledge all it needed was a running engine to be road-worthy. The paint on that car has a few issues, but I haven't spotted any obvious body damage. It is my intention to sell both cars, the parts, engines and manuals as a complete lot, rather than try to break up the collection.
Thanks for you interest, and I will try to get some better pictures of the engine in the car as well as the two in the shop for identification purposes.