I need some schooling on Gen 3 Hemis differences. Power v Reliabilty v $$$ v Fitting into a '68 barracuda fastback

Oh wow, they come with Holley dominators and an engine harness. That’s actually a really good selling point. I’m not sure if it’s possible with the dominators but do you guys lock the tune file, or do you let the owners have at it with a caveat?