The Neptune 3 Pro , max and plus all use the same extruder head , I have a 3 pro and this printed version doesn't fit well , there's a gap at the top , and there's a gap on the side , and the original fan housing doesn't work with the printed model , tried installing it and it wouldn't fit correctly , ( you can even see in OPs photos the original fan mount doesn't screw in correctly ) , it will work I guess but it's far from perfect , I appreciate the work the OP did but yeah needs some work , (edited)

UPDATE

didnt work with the origial hub holder , and the model OP made doesnt work , the fan dont all screw in the screw holes dont line up sadly , the extruder head needs abit of work honestly

Fits nicely, threads were a bit tight but better than loose. Little bit of sanding and convincing had them fit snugly.

einmal auf 70% skaliert und einmal auf 140%