Sorry about the table. It didn't come out as pasted. The system won't allow spaces. The top row is temperature in (F) and should be pushed to the right a couple tabs
The Shell Rotella T 15W-40 in API SJ formulation still has the ZDDP.
I saw the Moss motors oil, but think 20W-50 is too thick compared to the original 30W. At 140F, a typical operating oil temperture, 30w has a viscosity of 238 and 20W-50 has a viscosity of 396. The high viscosity and high resistance to flow will produce higher oil pressure. It will also cause less oil to flow though the engine and bearings. More oil will flow through the relief valve. Oil carriers away heat as well as lubricates.
Keith has had good results with 20W-50. It's hard to argue with success, but 20W-50 still seems a little on the heavy side