In latte 1960-s the Moskvich-408 was getting outdated compared to upcoming VAZ-2101. Because of this new car-family was started under codename “3-5” which meant that the serial production should have started in 1973-1975.
First prototype was Moskvich 3-5-2. As you can see from pics above it looks like (and it is) bigger version of Moskvich-408. It is lenght is 200mm and widht 100mm bigger. The main designer I. A. Zaitsev felt that current design is good enough so he made the car just bigger.
Also estate version Moskvich 5-3-3 was built. Also sedan modification with some different exterior details Moskvich 3-5-4 was built.
However by the time in 1970 when the prototype was made it was already aged design so totally new designt was needed.
Moskvich 3-5-5 is the new experimental model built in 1972. The dimensions were the same but it has whole new more modern body. Interior was the same as previous model.
In 1975 the next prototype was built. In this model the exterior was updated and the interior was totally new. It had automatic gearbox and 1,8 liter 103 hp engine.
Moskvich 3-5 series remained experimental.