Question on horsepower

So im putting in an engine because i blew my old one. This is a 355. Bored .30 over. Has a thumper cam in it. I dont know the duration. 650CFM edelbrock carb. Guy tells me its close to 400hp. Is this true?

It mostly depends on the heads, and the effectiveness of the combination. The heads, cam, intake manifold and exhaust must all compliment each other in order to produce maximum power.

So, with the information you provide, there is no way to tell power. It might go like a bandit, or it might be a mismatched dog.

Why is the previous owner selling it? Often, such used engine sales occur for a reason. Hopefully its not because the engine is a dog and the owner wants to start again.

Finally, did you see the engine run? If not, disassemble the engine and check bearings, clearances, cylinder walls, valves etc to make sure nothing is wrong. It would suck to do all the work of installation and find out its knocking, etc.