Careful! If the drivers pillar is bent, there'se a good chance that other thing might be out of line. I rebuild a written off Austen Montego years ago, but I had the benefit of a complete fabricatin workshop behind me, including jacking, welding and cutting equipment. My advice would be to steer clear unless you have a good knowledge of what you're doing. You could rebuild it, then find the chassis is bent, or the engine mountings have moved.
From what I know it wasn't in an accident, just vandalised (it was stolen and recovered). The pillar is my main cincern as I dunno how I'd get that fixed without having to fork out a fair bit. And qprdude's comment about the chassis has put me off the idea now really.
Tell you what, may be better to look at it yourself... if you search for E31 on eBay, it's the black salvage there.