Don't waste time with wedges, chains, blocks of wood. Even if these worked to get the crankshaft bolt out, as Slow-mo discovered, you've still got to put it back in. You're going to have to get it to 181 ft-lbs; your impact wrench isn't even going to touch that (and if it did, how would you keep from over-tightening?)
Just make the tool, fer cryin' out loud! There are lots of very good ideas on this site. I, of course, am partial to this one: http://www.yotatech.com/f116/cranksh...h-3vze-137934/
. The price was right.