Help quick, balancer bolt size???

Going to get a parts car today. I need to get the car running so I can limp it back home. Someone has removed the balancer. I have the balancer, but the bolt that screws into the end of the crankshaft to hold it on is MIA. Spending an hour under a car in the junkyard trying to break loose a bolt that's been on for 30+ years dosen't sound to appealing right now. I'd rather just go to Home Depot and get a grade 8 hardened bolt. So what size and thread is the bolt that holds the balancer on?

It's a '76 250. Thanks.

I think it is 3/4 x 16.

There's a dirty big flatwasher with it, too. Almost does more to hold on the balancer, than the bolt!

Thanks, I ended up just going to the junkyard afterall. Home Depot didn't have anything that looked remotely close.