Newer Aluminum W/P on '65 273 with A/C

Impossible. You can't bolt your sheet-metal timing tab to the new water pump since the inlet pipe sticks out there.

Look for my post a few years ago where I showed 4 different timing covers for SB's. I have never seen a sheet-metal tab for the driver's side, though there might be. You could fab your own. Interesting that one cover has an integral tab on the passenger side.