What is the difference between a 340 and a 360 and what year do they become classed as a mark-2?

Jus

In a nutshell - a 340 has a 1.4 or 1.7 Renault engine (unless it's a 343 DLS/GLS, but it's unlikely you'll find one of those) whereas a 360 has a 2.0 Volvo engine.

There's no "official" MkII designation - but we tend to call them MkIIs from Autumn 1981 (model year 1982) up to around 1985.

More detail here:

http://www.volvo300mania.com/forum-uk/v ... php?t=5363

Cheers,

Tom