I have a 1969 Oliver 1650 gas that has low oil pressure. I have used 20-40 and now 20-50 oil. I have had this tractor for 1 year and I was told it had been over hauled 6 months before I bought it, anyway the oil pressure is 5 lbs at 700 rpm and 18 lbs at 1800 rpm. I replaced the oil relief value and spring because when I checked it there was a small nut under the springs and the value was wornen. I have 150 lbs compression and no smoke. I plan on replacing the rod and main bearings, do I need to look for anything else? Model # 365-21024 and vin # 195-725-452 Any help is appreciate. Thanks