1973 GT and 1975 B

Why did MG put a dual carb in the GT version and a single in the B? I am brand new to MG's and just bought a 73 MGBGT and a 75 MGB. Both have the same motor, yet different carbs.
Thanks

The carburetor was changed to meet tougher emissions requirements. There are some
other changes between the 73 & 75 such as increased ride height
& rubber bumpers. Don't recall the complete list of changes.

Clifton

Thanks Flash75. I appreciate it.