Heads and cam swap
[email protected]/.520 lift will show a nice gain. I can't guarantee it'll make 360 hp, but it should be quite a powerful total street engine.
Your head selection will unleash the power potential very well with that cam.
A shame you can't squeeze headers in there. So to thtat end, make note of the exhaust manifolds casting numbers and check against the best one available. There outlet is IIRC, 2-1/4 inch. IMO, getting a dual 2-1/2 exhaust pipe exhaust bolted up to those manifolds would be very good for power output.