Dan, you're the best! Here's the measurements I can get with a ruler (dial calipers are out in the garage). Looks like it's an industrial one, that's for sure.

Total length of shaft from block flange surface on housing (just above the o-ring) to end of shaft: 3 3/8"

Mallory: 3 3/4"

Diameter of housing flange that goes into block: 1.300"

Mallory: 1 3/8" (1.375)

Length of same: 1 1/4"

Mallory: 1 1/2" from flange to bottom of aluminum billet.

Diameter of gear: 1.225"

Mallory: 1 3/8" approx.

Tooth count: 18

Mallory: 12

Shaft diameter: .515"

Mallory: 7/16" (.4375) approx.

Oil pump hex shaft: 5/16"

Mallory: 1/4"

This is a Mallory YL-679A