Welcome to the FMCA forum.
Good old 454's. Start by checking the vacuum advance unit mounted on the distributor. One needs to remover the Cap and the rotor to get a good look at at things, just be real careful not to pull off any of the plug wires if your not real familiar with the firing order of the cap connections.
Then connect a section of vacuum hose to the vacuum assemble, located on the passengers side, right side of the distributor. Pull a vacuum with your mouth, does the rod inside the distributor move in and out?
If not then the vacuum advance will not work. should everything work, then check the mechanical advance system. That is the system with the 2 springs one on each side are good and that the arms the springs are connected to mover freely in one direction and back again when released.
A drop of oil at each pivot point is good job while the rotor is off.
Post back your findings !
Should you not be familiar with this type system, seek some help.