Max,
Members of the group have PMed pictures and dimensions to other members in the past. I wish they had posted the information so future members had it available. Don't toss the cage. It is in perfect shape to ship by freight to someone who needs it. When I get back to Iowa, I'll try to get pictures and dimensions on my father's L600 cage. I'd like to put it on cad and post it so any local fabricator can build one.
From the manuals and specs I have, the L-516, L600, and L700 have identical frames. The cage should fit any of these models. The L-516 (which I've never seen or heard of) has skinny tires and bucket - 36" wide. The L-600 was sold as 36" or 42" wide. The L700 was sold as 42" wide.
What part of MA are you in? I've lived in the Boston area since '85.