Cost of an engine rebuid
Done right? Probably 3 grand or more just for the engine plus installation labor.
A used 2.5 NA is a far more efficient option than a full rebuild. But do tell, what's wrong? The common head gaskets, inspecting and testing both heads, new t-belt, tensioner and pulleys will cost you $1.5-1.7k through a knowledgable wrench. If the block is blown start over with an intact, dry used motor. If your candidate's heads are weeping now's the time to perform the HG resealing job to buy insurance for the future. Good luck.