Well, I had someone tell me that DIS was one of my worst ideas yet. My understanding was that DIS is more precise than HEI, and therefore cleaner, that it comes with electronically variable timing, allowing more efficient engine operation, and that the ICM was less prone to failure.
Some people have a 454 carb V8 from back in the '70's. Maybe they want DIS or a digital EGR. I doubt any computers are equipped for such.