1970 250--Rear Suspension Sitting Lower On One Side

[Jameel]

My 250 has suddenly started leaning towards the driver's side. Measuring up to the rear wheel arch its 1-1/2" lower than passenger side. Shocks in the rear are new this year, but I don't think that's the problem. I'm coming from a VW/Porsche background and know that a broken torsion bar can cause this. Can a bad coil spring on the 250 cause this condition? I have a Hayne's manual, and skills/tools to work on the car. I just need a bit of advice to get me rolling on this rather unfamiliar territory.