You should order this casting as A487 Gr. 4A (P No.3). The main difference is that 4A has a maximum tensile strength limit. Your foundry may be able to dual certify the casting depending on the mechanical properties, and then it would have a P number.
Be carefull overlaying with 316. Depending on dilution, you can end up with a martensitic composition, which would be crack prone. If possible, overlay with one layer of 309, and then one layer of 316.