Reply to "Tapping sound at bottom of oil pan"

Scott is correct- the pan must drop about 8" for the oil pump pickup to clear the internal baffle (your 'shelf'), then it moves 2-3" forward to clear other things. The crossmember and e-brake brackets MUST be cut- no way around it. They can then have flanges welded on so removal is simple NEXT time. This was a factory update a couple of years after your Pantera was built.
The position of the oil pump pickup is normally 3/8" above the inside-bottom of the pan. If as you say- the pan bottom is bent upward maybe from someone trying to jack the engine up at that point, the pickup is likely now touching the pan bottom. Noise will result. If so, oil flow to the crank and rods will also be restricted at rpms much above idle, starving the bearings.
The pump driveshaft has a star-washer on it that is supposed to ride about 1/8" below a cast block boss above the pump, to keep it from falling into the pan when the distributor is pulled. If the driveshaft is installed upside-down, it will do exactly what happened- fall into the pan. This poor engine really needs some internal attention by someone who knows 351-Cleveland engines!
I also think I see a twist along the pump diveshaft's length in one photo. This happens when even minor debris goes thru the gearotor oil pump that Fords use, and overloads the strength of the stock mild steel driveshaft. REALLY good, cheap insurance is a Ford Motorsports/Moroso/many others 4130-steel pump driveshaft- for less than $15. Good luck on what you find further inside....