rear coil spring

My '71 250C's rear slopes to the driver's side. I measured the height at the wheel wells and the left side is about an inch lower. Is a soft coil spring the only reason for this? The suspension mount rubber bushings are on my list to replace, could these be involved at all? Also, unfortunately, it looks as though that corner may have been in an accident (evidence of moderate Bondo repair), so what could I rule-out in terms of bent suspension parts?
Thanks for all your help,
Jason