Okay....it seems I have a good list now of what look for, thanks to all your guyses imput so far.
The motor mounts and drive shaft were replaced four years ago when the engine was rebuilt.
First thing I'm going to do is check the sparkplugs, wires and make sure the electronic ignition is set right. As mentioned, it could be missing too. Basically, I should just give it a tune up and see if that solves it. If not, then I know that I nned to go to the other steps.
Yesterday, I noticed that when I accelerate I still have the vibration, but when I let off the gas and coasted, the vibration was stronger. Now, I'm confused. This only happens on the surface streets. When I'm on the freeway at faster speeds, I don't get the vibration when I let off the gas. So this weekend I will be going down the checklist and see what I can find. Anymore, ideas will be appreciated.