Engine vibration/noise at idle

[ODBuffalo]

I just got a 79 with the 351, runs great, is quite and smooth. The one thing that Im concerned about is that when its in drive and idling, there seems to be a pulsating vibration from the engine. Once I accelerate or put it in park (RPMs change) its all okay. Only when Im sitting idle.

Any thoughts? Worn water pump? Pulleys? Belts?

Oil pressure and water temp all stay steady.

Thanks

 

[muddrivermike]

Is your idle maybe a bit too low when sitting still?Causing the engine to lope?Maybe you have to bring it up a little.