I've been learning from the board for 20 years and am just posting some knowledge back for people.

The MSD DIS coil-near plug box (6015/60153 and kits) works out of the box with the Holley/MSD dual sync distributors. But to use a Fast/COMP dual-sync the cam sync offset to the crank sync is wrong. I have a Comp 305005. You have to use the 50 degree reference, and change the firing order in the DIS to custom and offset it one cylinder. It becomes 8-4-3-6-5-7-2-1 on my SBC. This same adjustment seems to work for Terminator-X and all the other Holley EFI systems too.

The Holley dual-sync COP caps do not fit the Comp distributor even though they were a supplier at one time. Not the old cap or the new.

The DIS harness plugs directly into GM LS coil packs so you can use junkyard coils/harnesses with the DIS instead of buying the entire kit if you want. I'm using D585 coils and you have to use the LS2 setting in the DIS for the dwell to be correct.

Holley tech line said use LS1 setting and it's totally wrong. Here's how you won't know - the coils will autofire at 15 degrees advance based on the LS1 settings in the DIS. The lockout in the DIS to verify timing is 15 degrees. So the wrong setting will make it look like the right outcome. Picked up a good dial-back timing light and figured out that one out.