I just bought a high-mileage U4411 plastic base from a garage sale for $5. It cleans nicely, needs some touch-up work, a new headlight, and maybe a new belt and bag. I know it is an 80's model with the newer Hoover logo, large headlight lens, vinyl bag, and slide switch for power. What do you think? Pics are coming soon...
Personally, I think you got quite a deal, finding a Hoover Convertible for only five dollars! Being the owner of two Convertibles myself (and a very similar Guardsman), you will be most impressed with its performance, as well as its longevity!
Below is my model U4303, from 1980, which is of the same design as your U4411, and is still going strong.