bolt that holds crank pulley on needed

It's fairly rare to have a slant 6 with a balancer bolt. The only ones I remember having them from the factory are some manual trans vehicles....mainly trucks and vans with the double or triple groove balancer. Like 65Dartman says, if you're worried about the balancer coming off, you can use a small block bolt if you add a couple of washers. You'll need to clean out the threaded hole real well and maybe run a thread chaser in it. In 40 years of working on Mopars, I think I've seen 3 slants that had a balancer come loose from the crank.....all from improper reinstallations where they cracked the hub.