273 cylinder out

A little help from the Mopar Gods ?
My 273 seems a little low on power ,so a cylinder is kinda dead,if I pull of the plug wire the is no difference in running however the plug is firing.a compression test showed the cylinder to be a bit low but nothing to be concerned with,no oil smoke,I took the valve cover off and all is operational under there.
Now I do not know any history on the car ,but was told buy the dealer who sold it to me it has 318 heads on it,,,,,any of this sound right ? what am I missing to do ?