Efi Magnum Swap In Progress Early Plymouth

What sort of HP can you get from the 360 magnum using the factory intake and efi?
I have done a swap but went to carby as I didn't have all the bits. Will be doing another one soon and interested to keep it efi. I have 420RWHP currently so I imagine it would be in the high 500s at the fly wheel. Is this achievable with the factory manifold and ecu?
thanks