The
Riviera came out in 1950. The 16' Riviera with 60 HP...The 18' Riviera with 131 HP, and the 20' Riviera with 158 HP. The last two with ... 6 cylinder "In Line" engines.
The picture in a previous post has a modern "Closed Cooling" V-8. The upholstery does not appear to be "correct" as the original was "Dark Red"

NB
REF: Robert Speltz:
The Real Runabouts. Vol I & Vol III.