My first magnum build, advice appreciated

The SCT tuner would have to be purchased through whoever does your tune. If you order tge tuner from Summit, it will be blank with no performance upgrades. If you get it from someone who does the tune, they will build a file to plug in and load into your truck. I see that Summit does have Diablosport listed for Magnum engines. I was under the impression Diablosport only did diesel engines for those trucks, and gas engines for newer Hemi trucks. I got some research to do.