It doesn't matter what year your Omniums are. You're not supposed to use spacers because the included BB was designed for use on a 68mm shell and the spindle attached to the drive side arm's length reflects that. Unless you have a way of magically lengthening the spindle to compensate for the 2.5mm spacer, you can't properly install the non-drive side arm when using a spacer on either side.

Also, would you mind telling me how putting a spacer on the NDS would possibly have any effect on chainline? Here in the dimension where I live, it wouldn't.