That is the exact problem I had on my 307. It turn out to be a bad distributor. It turn out the bottom part of the housing on the groove oil travel around it, then into the lifter gallery. It did not seal properly, and it leaked back into the oil pan. Let me tell ya, It was pain in butt looking for that low oil pressure. I replaced all the bearings and still the oil pressure very low. The pressure read 50-60 psi cold, and 5 -10 hot at idle. After replacing the distributor the oil pressure jumped to 80 psi cold 40 psi hot at idle.
Hope this will help you.