Front View
One example I own has two untapped Z bar stud provisions.The other example has no bosses.

Part #
Part number Date circle and mold number are cast into clutch fork hole knockout on the passenger side.

Top View
This view shows the top with the GM logo cast just above the transmission mounting flange.

Fork Side
Fork hole is the same as Most Chevrolet aluminum clutch housings,and accepts the14007355 rubber fork boot.

Inside
This picture shows the typical  inside webbing, And the straight starter side that identifies it as a 153 tooth bellhousing.
  These housings utilize a stamped steel inspection cover, that is attached via the four 1/4"-20 tapped holes along the bottom edge.

Bottom View
In the Chevrolet parts manuals dated after 1980 ALL  3858403 part numbers are followed by this notation ( IDENT.  NO.  3840383 ). Some beleve that the "383" bellhousing was the early part. This may be in reference to the 462606 bell that has 383 cast on the clutch fork ball stud boss of some bells.