There is no such engine as a "62 Chevy II 235". The Chevy II engine was a 194 cubic inch 2nd.-generation design similar to the 230 and 250. If the back of the block is shaped like a Chevy V-8, and does not unbolt, you've got a late model inline 6.
Loss of oil pressure when an engine warms up is almost always associated with worn rod bearings, ditto on the rattle on a "float", neither accelerating or coasting. I'd suggest dropping the oil pan and inspecting the rod bearings. It might be possible to change bearings before any further wear happens, and there's a good possibility the crankshaft won't need regrinding. If the engine continues to knock, the crank will be damaged, and there's a possibility of a rod bearing seizing up and doing major damage to the engine.
Jerry
