Is that 5-speed compatible to a 603? I'm pretty certain its a no-go on a 616-617.
If I were shopping for number three, and rust was the biggest issue with my other two, I wouldn't want a rusty trifecta. It seems almost masochistic.
Plus you don't want to be on "Hoarders" for a Mercedes parts collecting addiction.
No offense to Hanno, but the car seems way overpriced to me. The only valuable part is supposedly the 5 speed, and with bad paint, rust, a motor that could fail any day, etc, its a sub 1k parts car.
You can do better.