I purchased 1987 4.9 L recently. I have two symptoms. One: a oil leak front of engine; which I believe is front main seal. I degreased engine and it appears to be coming from there. Second symptom is a on again off again noise that sounds like it may be bearings. At first I thought it was power steering pump. But after searching on net and reading threads I'm thinking it may be something behind timing cover or harmonic balancer. Any ideas???

 

It's possible that the harmonic balancer is going out, and that'll make some noise.

As for the oil leak in the front, about the only thing up there is the timing cover. A timing cover gasket set includes the front of the oil pan gasket (since they touch), the gasket between the cover and the block, and the front main seal around the harmonic balancer.
The whole kit (get the more expensive of the two) is about $15 - $20.

I did mine in a few hours. Takes removing the radiator and the fan, as well as a good puller for the harmonic balancer. If the balancer comes off in two pieces, you know it's bad.

 

Thanks for the help.