Guys, we are talking about a 11.50 second 440 with hyd. cam

Bought the car a few months back, I don't have very much history on it, now it started making a very loud moan/squeal only at idle, if you bring it 100 rpm off idle it's gone. Seems to be coming from the back of the engine/transmission area.

I have ruled out the water pump & alternator bearing being shot. It also doesn't matter if it is in gear, neutral or park.
Any suggestions without tearing it down? Would you lean towards engine or tranny?

Thanks in advance