@Mike-BBQ I'd start experimenting. For starters, consider getting the food grate up above the normal grates and put a sheet pan under it for drippings. I've used all sorts of things do do this even when I had a pellet so I could get the meat up and away from the heat and get a drip pan under it.
Work out your temp. I think 225F on an E425 can be done with one burner on low, maybe medium. If you need two burners, use the outer two, and get the meat raised up in the center.
Since the center burners are off, put a couple of smoke tubes under the main grates directly on the flavorizer bars. I've used pellets but started using wood chips. I get pecan chips online from amazon. Post Oak has been harder to find.
Do you have a good remote thermometer ? If you can measure grate temp with the food grate raised up then you should be able to dial in the temperature. Once you know what it takes, light the smoke tubes and get some meat on.
As far as things to raise up the grates, I used extra flavorizer bars and I've also used fire bricks. I might have pics somewhere but I think you'll get what I'm suggesting.