What's With This 360 ????

360 sat for a long time. Engine is stock.We hot tanked it. Cleaned it out again, all good. Honed. New rings,rod bearings,mains, cam bearings and lined up correctly. All clearances .002 with plastic gauges. All plugs accounted for. 2 New hv oil pumps. 2 new oil filters. Primed with drill, 60 lb. Both banks oiling. Started engine, 60 pounds cold, 20/50 Rev tech oil. Once engine warms up oil pressure steadily drops while holding it at 2000 rpm. Less then 10 at idle. Won't get over 25 when we rev it up. Number 7 lifters, intake/exhaust always clicking. All other lifters good. installed new comp hyd. lifters, still number 7 is clicking. Cam, is not wore off. Soaked lifters in oil and pumped them before installing. Rocker shafts are installed correctly. Bottom end of engine solid. We are thinking there may be an internal crack in this block. We've done Many,many Mopar Engines over the last 40 years and haven't seen this before. Give us your thoughts.