Re: Uneven porch floor suggestion
If at no time can the floor get wet, either from open windows or (and this happens a lot) the original sleeping porch floor boards extending to outdoors, you can do anything you like or can afford. You could correct the slope with shims and/or sleepers, and lay a fine wood floor or laminate or carpet,(maybe there isn't the necessary framing stiffness factor for tile).
But if the enclosure back in the 50's left the old porch floor ends exposed, you have to worry about letting the moisture that comes in there still be able to escape. A wood-to-wood sandwich, then, should be avoided; the sleepers would still be fine because that leaves a space for air movement.
If you wanted to preserve the old-school sleeping porch theme, you would get back to the old wood deck, and cover it with canvas, and then paint the canvas.
Remove not the ancient landmark, which your fathers have set.