George Stauffer was a big proponent of swapping the Cleveland for the Windsor; lighter, easier to work on, more parts, etc.
I did buy a pretty good 73 "L" from him with the Cleveland. The mods were an Edelbrock Torquer intake, Holley 750 instead of the auto light 4 brl, the GTS headers, and the basic cooling kit (which was indispensable). No comparison to a GT, BUT, I could pretty much dust anything contemporary. I had a friend with a pretty stout 69 Vette, 427 Tri power/435 horse. He couldn't get over how my Pantera ran from 100-150. For relatively cheap stomping' fun, you can't beat (or at least you couldn't) a Pantera. Parts are available, mods are relatively doable, and POCA members will help you with about anything.
I think the initial build quality on the 71s, especially the push button cars, sealed their fate. The cooling issues didn't help. The rust was probably the final straw. However, if you find a solid car, and you do your homework, you'll have a ton if car for the $$. Problem is, they're still 40 years old...