Stock non adjustable rockers will work just as long as the push rods are the right length.

I would use the adjustable 273 rockers, they are stronger and will allow you set the preload exactly where you want it. Easier than getting the right push rods especially if all 16 push rods at the same length don't work for all 16 with non adjustable rockers. What if one push rod needs to be longer or shorter than the rest when you check pre load? Then adjustable rockers come in handy.