i just bought a k20a2 for dirt cheap. the head was being rebuilt but im new to building an engine. what should i do when rebuilding an engine? what things should be replaced? what should i look for? should i clean all the parts (acid wash or steam or lots of carb choke cleaner?)? i just got a service manual. what things should i keep in mind...

what can i reuse from my old engine (k20a3)? all i have is the engine block, a head, oil pump, water pump, and some other things... what else would i need for this swap?