To hot exhaust manifold on 360

Picked up a 68 270 with a 360 from previous owner installed. Been sitting for 3 years. So changed the cap plugs rotor and wires. Set timing seemed to be I'm running. Took for a spin and hot exhaust. Kept messing with timing bought a vacuum gague to help set timing. Still hot exhaust manifold. After a week of playing with it i finally realized I was off by 1 plug on the distributor. Thought you would all get a good laugh about this.