LA 360 or Magnum 5.9

You can put 1.88 valve heads on your 318 and 350 HP should be as easy as falling off a log.

The hydraulic roller is OVERRATED. In fact, I stopped using hydraulic roller lifters over ten years ago.
For what you want to do a decent hydraulic flat tappet cam would be more than worthy. If you don't mind lashing valves, do a SFT.

Use what you have.