Steve,
If your range fan is like ours, you should be able to pull the fan blades off and put them in upside down (or would that be right-side up?). Basically, reversing the fan blades to blow out. Our fan just slips onto a D shaped shaft.
It's interesting that your two fans were different. Ours were exactly the same. Color, diameter, and motor all matched. I do think you hit the nail on the head with the comment about ball-bearing fans. The original motors in our rig look to be brush-type motors and when I manually turn the fan shaft you can feel quite a bit of resistance. It's probably the reason that they are so noisy, not to mention have such a higher amperage draw.
I'm also going to keep your warning in mind...we don't need any extra odors being sucked into the rig
Fred