Thank you for the replies but having knocked the oil pick up screen and wire retainer loose on several of my futile attempts to seat the oil pan , I decided to bump the the oil pickup canister with my fist and discovered it easily moved rearward about an inch. The oil pan then was able to seat against the block. Celebration was short lived as I discovered engine still ran with a slight knock after fire up . I'm not experienced with babbit pounders but am now wondering if my choice of 10-30 valvoline conventional oil is too light or if the engine just needs a rebuild as one or two of the connecting rods were down to only having one shim left wont none on the opposing side. Also it does blow some smoke when I warm it up to 180 and rev the engine. The truck sat in a yard for about 20 years before I bought it.