FC Thermoswitch P/N???
 

I searched & found plenty info on the advantage to installing the FC thermoswitch, but no mention of the P/N

I looked through the Mazda Motorsports site & came up with PN41-18-840. Is this the correct p/n to order?

Thanks,

Yes. Pn #41-18-840
It'll probably come in a box marked "air temp sensor" or some such, so don't let that throw you. If it's the correct one, it will be stamped with a '95' on the body, instead of the '108' for the OEM FD sensor.

From the FAQ thread:
https://www.rx7club.com/3rd-gen-archives-73/fc-thermoswitch-fd-447606/
Dale Clark is the da man :)