Hi, I'm having a strange problem maybe you guys can help me out with. I have a 1972 f100 with a 360 in it, while driving home from work last week the oil pressure gage went to "L".  I did notice a lack of power when going up hills as this was happening but no other out of the ordinary things. The truck has always ran towards the low side even after I replaced the oil sending unit.  Once I got it home I parked it, didn't check the oil until the next day and it didn't show on the dip stick. I decided to drain what oil that was left ( 1 to 2 quarts ) put a new filter on and fill it back up.
     The truck started up and ran fine other than smoking a bit, it hadn't done that before. I drove it maybe 5 or 6 miles and the oil pressure was good, better than I had ever seen it.  So a day or so later I drove it about 12 miles at a constant 60 mph. Around about 10 miles I noticed the oil pressure gage started heading towards "L" and the just flat lined. The truck lost power but I was able to limp to a parking lot.
     I looked under the truck and noticed oil dripping from the bellhouseing. I checked the oil and it was not showing on the dip stick again. I let the truck sit for an hour and checked the oil again now oil was on the dip stick up to the full mark. Started it back up drove it back home and the same thing happened again lost oil pressure and power. I lipped it home to the garage and there it has remained.
     I took the valve covers off to check for any obvious signs of obstructions in the oil return passages but could find none. What do you think is going on with this thing?  Thanks