What is the size of the opening in the shroud?
Probably also ought to carefully measure if the center of the present fan is in the exact center of the shroud opening.
A ten percent larger diameter fan does not move 10% more CFM.
It typically moves
1.1 x 1.1 x 1.1 = 1.33
at least.
The power taken from the engine typically increases even more
1.1 x 1.1 x 1.1 x 1.1 = 1.46
or 46% more
Above assumes fan design and number of blades at pitch angle
stays roughly constant
Power laws of fans routinely surprises
The bending of blades in a flex fan make them unpredictable especially as age makes the material either stiffer or looser.
In past posts here on Moparts is a graph of rpm versus kilowatts comparing the solid fan versus viscous clutch fan of the original 340 V8
The plastic multibladed radiator fan of later model year Cummins Diesel Ram trucks looks like a computer aided design that might be significantly better than older designs.