block identification concern

That is a RAISED block industrial / heavy truck, with the high mount water pump. No idea CID but it for sure is not a 400 low deck

The heads / intake are completely different. There are ports on the fronts of the heads where the water pump mounts, and the exhaust manifold/ ports are different. On some of them, there is coolant runs in the intake/ heads where normally would be the heat crossover.

Look at the photo showing the rear of the engine. There's a coolant block-off plate on the rear of the heads, which if reversed side to side, would become the front of the heads.

Notice the oil filter/ pump!!!!