Fitting a blade disc is feasible with a new disc and blades from a mower with the same cutting width and the blade boss.
The problem I see with doing this is the mulching function will probably no longer work well at all. While they are not the best the blade bars are not that bad, they are thick enough you can sharpen them many times and long lasting.
As to your vibration I would be checking to see if maybe the crankshaft is slightly bent, to cause noticeable vibrations you should be able to visibly see it by comparing the height of the blade as compared the the mower deck on one side, turn the engine over 180 degrees (SPARKPLUG LEAD OFF) and comparing the other side of the blade to the same spot on the mower deck.
