3.5 is the cabby only, basically a mk 3 with a mk 4 front, came out when the mk 4 did if you get my drift illuminates inside like a mk 4 but has mk 3 dash... VW obviously couldnt be arsed to bring out a whole new car and just modified the mk 3 cab
also has better wing mirrors
i know a few people who have put this front on their mk 3, not really my bag as u may awell just get a mk 4.