Q: is the rear lowered by torsion bar if so how is this done
A: I only know that the YEAR of your 306 may make a difference in answering you. Phase ONE 306, 1993-1997 had mostly rear drum brakes, perhaps the rear disc brakes were an option. Phase TWO 306's, May 1997 - 1999 UK - 2002 Europe, had rear disc brakes. I only have a Phase ONE to look at and advise you, IF this is your car? Hear is a chart showing the different "ride heights" for the Phase TWO 306 (N5 in Australia). Depending on engine code and body style, the Road-to-jacking point differs. See the last two charts on this website: http://www.peugeotlogic.com/workshop/wshtml/mechanic/306susp/306align/align306.htm#4