Very impressive! You can make more power with what you have, but it will require a fair$$$$$ investment.
A ported 3x intake, higher lift cam, optimal headers, bigger cam core, the list, and cost, never ends. Your motor appears to be about the best ,or on par with the best, i have seen on here for a 440-1 head. I made 926 hp, but had fuel injected methanol, bigger cam, ported intake, to name some things that gave my 550 inch motor an edge. Your torque might outrun the hp i made as well!!!