I'm sure somebody out there will have another opinion, Jay but I'd go with the 18.25" fan. I haven't seen many pump mounted fans that ran anywhere close to balanced, so I would leave it be. Good luck!
The 18.25” fan is a good size but the outer layer of the fan blade sandwich isn’t indexed. That might be dangerous. The 4 bolts function as another form of alignment, so it might be ok. Another option would be to look for another fan spacer with a longer button on the end. That would solve everything.
It’s installed and no noises, so I’m happy. I could seal it up better where it meets the lower core. The pic shows some daylight coming through. It might not make any difference. Now would be a good time to add a warning sticker at the top of the shroud to avoid finger loss but the uninformed.
Link to video. More advice is welcome.
