Yes, it fits straight in, but you will need to use the 600 inlet manifolds as they are different to the 750 ones, even though the carbs are the same.
Gearing will depend on the year of the engine as the primary gear ratio changed, but is not a problem. The 600 and 750 CDI units are interchangeable so that's no problem either.
As Kev says, it might be worth getting the race committee (?) to ok the 750 frame to prevent any issues later on, but I can't see there being a problem.
Good luck and give me a shout if you need any info.
Cheers, Paul
Paul
15th year in DD #68 and getting slower by the year
1199, SS800 & 620SSie DD racer