OK, now I'm a little confused.

So should I hook up the 2-speed harness to the 3-speed switch? If so, should I use the two separate plugs (two and four prong) from the 2-speed harness, or re-set the wires from the 2-speed harness into the 3-speed plug (6 prong).

What would happen if I installed the 3-speed wiper motor and just kept the 2-speed switch. Or instead, added the 3-speed switch and just left off the red and green wire. (If I plug the 4-prong plug from the original 3-speed harness, that will eliminate the red and green wires)

Finally, if I can get my hands on a variable switch, that would work properly with re-setting all of the wires into the 3-speed plug?

BTW, the 3-speed switch I have is 3488764. There are three clicks so I don't think it's variable.

All help appreciated!