bolt that holds crank pulley on needed

Cudamark: so you think I can run it without the bolt? Thanks for your patience. The treads do look surprisingly clean;
If it's been on there for years, I'd leave it the way it is. When I pull one off for any reason, I use a small block bolt to reinstall it and then just leave the thing on when I'm done. But then again, I have lots of extra small block balancer bolts so I don't have to go scrounge one!