If you're going to make up your own suction unit, the Lamb Electric
"Acustek" vacuum motor #116025-13 would be a good one to use.  This is a
two-stage by-pass device rated at 91.5 inches of water when sealed, and
102 cfm through a 2 inch orifice, continuous duty.  "By-pass" means that
the air used to cool the motor is separate from the vacuum air, so that
the motor keeps cool even when there is little or no air flow through the
vacuum side.

The "Acustek" models are up to 10 db quieter than the standard ones, and
in my 2-year-old copy of Grainger's catalog they're a little cheaper at
$62.65 each.  They can also be used as blowers just by reversing the
input and output. In that case the by-pass prevents the motor heat from
warming up the blower air.

Fritz Gellerman