At 14" of mercury at 6000 RPM that blower might take 100HP or more.
You might look at the Roots style blower for a example of HP draw.
45 URAI Roots Style Blower | REP Inc
The PDF will show the HP curves. The flow verses vacuum is about the same for all rotary lobe pumps.
You can still use the pump you have but I would think you may only be able to drive it at 500 RPM or so depending on the vacuum pressure you need.
I do have a extra Roots 33 blower that has been sitting out for a few years. I don't plan on using it and it is rusted inside so it wont be good for hi vacuum but I would take $30.00 for it.
I'm in Phoenix.
Good luck.
Dave