The Chevy 350 uses a V-8 block so the camshaft is located lower than the heads, in the center of the engine block. A camshaft is a long rod with lobes, or cams, that push rods to open and close the valves in the heads. In the 350, the camshaft is driven by a chain. The timing will need to be set again, and it is a good idea to install a new chain as old ones can be prone to slipping and may cause damage to your newly modified engine. Camshafts are designed to perform the best at certain engine RPMs, so it is best to choose a camshaft that fits the heads you have chosen. A top end camshaft will leave the valves open for different amounts of time than a low end one, so mismatching parts could be dangerous to engine performance and how long the engine will last.