The 749 / 999 is an evolution of the 748 / 9**. Keep the 2 styles different, I don't think they mix.
I bought a pair of Casoli twin carbon cans to fit my 749 that were styled on the 748 twin termi cans.
Spent half a day fitting them, started the bike, stood back and looked at them. Then spent the next couple of hours taking them off. Did not even ride the bike it looked so wrong.
Thank god for E-bay, sold them for more than I paid for them