This is correct; the US-spec Series III was no longer a full-blown trop-top, it didn't have vents or alpines, it only had a sunsheet. A PO of mine swapped mine for a full trop-top.
Around '68 or so, the wheels for Rovers for North America were 15" wheels, and 88"-only anymore, they quit bringing in 109", and quit the 16" wheels.
They also cut back on color options: marine blue, pastel green, limestone, and poppy red were your choices.
The best summary I can think of off the top of my head would be ECR's:
http://www.eastcoastrover.com/INFOSeriesIIIUSA.html
Also, there's a bit on LR-FAQ:
http://www.lrfaq.org/Series/FAQ.S.ch...ering.259.html
FWIW...
-L
'72 SIII SW 88"
'60 SII 88" RHD