My friends shop burnt to the ground last week, it was a total loss. In the shop was a SBC stock block that I was building. The only work done on it was a clean and mag. No machine work. It was in his shop because he had the tools to drill out and tap the oil galleys.
The block was on a brand new engine stand that the paint burnt off. However it had a brand new set of ARP main studs in the box on top that survived, the box was burnt some.

Anyone have experience with cast iron engine parts going through a fire? Did you use the any of the parts after the fire?
I’m going by to see my machinist today to see what he thinks.

It probably could be used especially if you’re going to send it out and have it machined but if it’s just a stock block and not like a numbers matching for something is it worth taking a chance

At our store we use an Oven system to cook the block about 450-500 degrees then shot pean it, I think you will be fine but I'd have it magged again just as a caution.

Can not attest to iron block. We had first funny car burned in garage fire when it was being worked on by man we named car after. Garage burned car being in middle of it and source for fuel for fire. We used every piece out of it aftger rebuilding.

I would think if aluminum and magnesium parts came out fine.Iron block should be fine.

If that cardboard box the studs were in made it through then it didn't get that hot. You could hardness test it in a few places and compare to a known good block. It sounds like something I would go ahead and run. JMO