SOHC engine identification

[JT191]

How do you visually identify the difference between the G161, G161S, and G180S engines?

Were all these engines available in Australia?

The photos I have found show:
The G161 plain has a rectangular valve cover that appears to be a steel stamping.
The G180S engine has a multi piece aluminum valve cover with the top plate angled away to the right side of the car.

I have not found much about the G161S. One photo shows it is identical to the G161 plain, and the only diagram I found is a cutaway, and may show it looks very similar to the G180S.

Does the G161S have the same appearance as the G180S?

[JT191]

From what I have found, there appear to be at least three and possibly four generations of G series SOHC engines. The displacements are mostly the same across the group, making it very difficult to sort them.

Hillman
GH10 (1265cc)
GH150 (1494cc)

Early Bellett Narrow Valve Cover, 2 Bolt - intake and exhaust on the left and spark plugs on the right
G130 (1325cc)
G150 (1471cc)
G160 (1579cc)
G161 (1584cc)

Later Bellett Narrow Valve Cover, 10 Bolt - intake and exhaust on the left and spark plugs on the right, multi-piece valve cover angled toward the right
G161 [S?] (1584cc)
G180 [S?] (1817cc)

Gemini/Piazza 4 Bolt - intake on right, exhaust and spark plugs on the left, wider valve cover stepped back on left for spark plug access (1976 and later?)
G161Z (1584cc)
G180 (1817cc)
G200/G200Z (1949cc)