The CB450 carbs were an early version of a CV carb. They also used a 2 into 1 throttle cable assembly. They were connected together only to actuate the choke butterfly.
In order to install four of them on a CB750, you'd have to come up with a 4-1 throttle cable assembly and figure out some way of connecting together all of the choke assemblies.
Even after that, I can't imagine that they would be much of a performance improvement. Any of the people that I know that race CB450's in vintage racing replace the CV carbs with some Mikunis.
Tracy