help 1964 Slant 6 tune ups specs

2.5° ATDC is wrong. That's 5° retarded from the correct factory spec of 2.5° BTDC, and it's 7.5°*retarded from the 5° BTDC setting that works well in most cases. The '64 timing indicator setup has the timing indicator on the manifold side of the engine. If that's the setup you have, then while you're standing on the driver's side of the engine bay looking at the timing marks you need to move the mark upward to advance, downward to retard. If you have the later setup with timing indicator on the distributor side of the engine, you need to move the mark downward to advance, upward to retard.

Do get the three books described in this thread as quickly as you can.