Hi JohnAh some of my family heritage goess back to Sweden
Anyway yes you are on the right track with the type of car and one is the ST10 built 1976 the other is the ST20 built 1977
The ST10
The ST20
Yes it is a modern two stroke for its time with the seperate oil injection and reed valves on the intake.
This motor puts out from 28hp-33hp depending on model it is known to be in a very low state of tune from the factory it is said our old two stroke lawn mowers have a better tune
The last of these motors had the oil injection to the cylinders deleted and are now known as low smoke motors and that is the type i got as a spare.
Cheers Jamie