Pretty sure I have this backwards. I was planning to run the Magnum EFI on my LA and was thinking about a different flywheel in case the front mount sensor setup I hacked together didn't work. I think what I ran into was that there was only one manufacturer that made a flywheel with notches for the sensor, but it was balanced for a 5.9 and wouldn't work with my LA motor.
I went round and round with a guy from Modern Driveline about this. They show (showed?) a flywheel part number MD-LBS360LA-130T that the guy swore was right, but I was never really sure. They do show a flywheel for the 5.9 with notches though, so there should be an option for the guy that is running a Magnum.