All you can modify is the heads. Blue print the carburetor. 340 cam. I would not use 360 heads without changing the pistons and then I would have the block decked.
Guess it comes down to how much cam can be ground out of stock one
Heads flow should be easy enough ported even with 1.78 valves, decent cr should be able with machining, two barrel and manifolds be the most liability, should easily make more than 318 hp.