Dunno...... You might be onto something, but my gut feel is that it won't work.... at least not for very long.
It does say on the 2nd page of the AEM manual that the 4 channel box is suitable for systems with 4 ignition coils, and the 8 cylinder box is for systems with 4 or more ignition coils.
Then on page 16, it says it's for engines with distributorless ignitions.
If you run this from the ECU, and keep the distributors you'll have 2 channels working twice as hard as they would be in normal waste spark mode, and I think you'll be letting the smoke out shortly......