Cooling System Redux - Blower Motor

So after a quick trip to OSH to pick up some supplies, look what I found. No diagrams, no drilling extra holes, no aluminum bar and no pilot hole...just a perfectly centered, 3 1/4" hole. Awesome.

The key is the center shank (as seen in the smaller hole saw) that allows one to replace the dinky pilot bit, with a hole-saw that is turned around and acts as a large pilot bearing for a situation when you already have a pre-existing hole.

Now the setup wasn't cheap but I already had the 3 1/4" hole saw and 3/8" chuck shank for som work I did on my entertainment center. The extra $45 it cost me for the 2 7/8" hole saw, the replacement pilot shank and the tiny threaded adapter ring (highlighted in the red circle) took a two day job and made it 5 minutes.