Engine stand to engine block bolts

The answer is maybe. The bolts that are used normally have a threaded area then a longer blank shank which is usually longer than the stands mounting plate. You could stack washers on the bolt to make them work but make sure that the shank is recessed in enough. Then be sure that you don't over torque them as you could strip the hole in the block. The only other issue is if they used a special head on the bolts, some use a reduced size for better clearance and those are designed to simply hold the transmission to the engine with the mounts holding the weight, for those you will want to use a standard style bolt to get the larger surface area.

It will need to be replaced. That pin helps hold the balancer in place to allow timing and belt drive without relying only on the taper of the shaft and bolt. They combing to hold it. The pin should only be a light fit so if you can get a small carbide bit to drill a small hole in the broken piece to might be able to remove it that way. I would drill a hole, then insert a small threaded screw and try to extract it.

Yeah it isn't going to be a fun thing to replace. The other option would be to use a drill guide and drill it out but that is a really touchy thing because and alignment issue will cause problems. Oh, and if you try to use a lot of heat you can damage the seal and the main bearing. What is the issue with the original engine?

Well, worst case would be to check the other crankshaft and if it's okay you could have it ground if needed and swap it over with new bearings, or if you can't get the pin out pull that crank out and have a shop try. They could also do a different option which would be to install a short pin to use as a locator pin and then drill a new one through the balancer and into the crank snout. That would do the same thing to give it support.

In that case I'd let them deal with it. Good luck, let us know what they do.

It holds the pulley from moving, if that pulley starts moving on the end of the crank, it chews up the end of the crankshaft and the pulley as well. No different than the camshaft sprocket keyway just inside the cover. They use a pin on those because of the seal being there, on other engines there is a key for the damper, all for the same reason.

"Efficient design" is their thing. These days it's everywhere causing problems.