John, that is a bit of fun history! I had no idea that Hoover made that many changes in one model. You are right, mine must be an '85. It has the 4-position height adjustment & bottom-fill bag. I thought it looked like it might have a type A bag when I first spied it,but it's good ol type C.
I also to look at pics of the other models you mentioned. The U4363 was the model that my mom & grandma both had long ago. Theirs were earlier models though I think. I believe my grandmother purchased them both at the end of the 70's or very early 80's. I was remembering the color of their's to be this shade of blue, but it may have actually been more turquoise for the hood & bag color.