Engines A90537 were manufactured in the same three styles as the 8 cyl above.
Most differences between supercharged and non-supercharged engines are internal and not covered here.
Details of the supercharged engine internal differences can be found at:
There are two external identifiers. One is the engine serial number begins with GH. The other is a hole on the bottom of the left side of the block, slightly forward of center, that is for an oil drain back tube fitting.
UPDATE NOTE – Since this engine was restored it has become known that the superchargers were delivered to Auburn by Switzer Cummins painted black. Auburn did not repaint them green. All superchargers should be black on the green engine.