I have what looks like a water in the oil problem. Just discovered it as the temp
gauge started jumping up and down, was low on coolant, oil looks like that's
where the coolant went. I think the bearings are still ok as only drove maybe 15
miles. Likely is either intake manifold or head gaskets. I parked the car and
drained the oil. Question is if it sits for awhile (like six months) is it best to
leave it drained or put in new oil or doesn't it matter?

drain the coolant. fill the motor with fresh oil (use some cheap stuff for now). start it, run for 15 -30 seconds shut it down. let it sit for 30 minutes and drain the oil, change the filter and refill with good oil. run for anothe 15 seconds. store it. you have to flush the water out of the system.
it is really best to fix it now then run it and be sure the oiling system is clean before storing it.
to really flush the system, you really need to run it a while with a few oil changes, to be sure. just that quick flush tho is better than nothing.

Everything said above is correct. Remember, you do not have water in your oil, you have coolant. Coolant is death to bearings. In a 2.8 it is almost always the intake leaking into the engine. Many people think it is the headgasket and just happen to fix it because they also take the intake off to replace the head gaskets. Remember also, if you leave it sit you will be allowing more coolant to be dripping into the oil.

Thanks for the good replies. Yes, it is a 2.8, '87gt.