Have a 1980's vintage Homestead Superfan 4000 that has been in storage for 13 years--while attempting to hang it, the middle of the flywheel crumbled due to age--part had the number FH6-A on it--replacements on line say that part is no longer available but is replaced by part FHS66M which looks identical in size but has many more screw holes--anyone have or know where I can get an exact replacement as I am not sure if that replacement part is going to work?

It makes sense that your flywheel is no longer available, especially when in fell apart like it did. Same size more holes, sounds like one part fix many fans. Check out the return policy or contact customer support. Pay with a credit card, cross your fingers! You may be able to find a measured drawing of the part by searching images. Sounds like you've found your part.

I think that is the motor/fan coupler, more of a U-Joint than a flywheel. Problem with older fans, even those used a lot and not just stored. I never try to fix. Simplest solution is to get a new fan if the replacement coupling doesn't fit. The reason for so many holes is that the are used on 4 and 5 blade fans.