Car: 1989 Buick LeSabre Custom

Whenever I am in gear and accelerating, the car makes a clicking noise and sometimes there's a vibration coming from the engine. It does not do this when coasting or in neutral. The clicking gets during acceleration gets worse the faster the car goes. I've been looking under my car for some clues, but I did find an oily 5/8" bolt near the car. Any advice?

Engine/trans mounts, CV joints, lifters, harmonic balancer, loose torque converter bolts & cracked flex plate are just a few ideas, based on the limited information available.