I'm running a 400 dodge on propane, timing is at 10 degrees (from 8), true duals, 2bbl intake, open element air cleaner and am making just as much power it does on gas. Anything that woud give more power (cam, headers, etc.) are a bonus. Swap to a 4bbl if you don't already have one too. Imco 425 mixer is a good one. At worst you could have to throw cats on.