318 Timing Question:

Working on a car that has been sitting awhile and have no history on it.
Starts up and idles fine, but is real rough on acceleration.
going thru the basics when checking the timing, the timing mark on the balancer does not show at all, checking TDC and rotor position it looks to be a plug off.
I,m thinking the timing chain skipped, it has 98K on it.
Any opinions?