anybody know the difference between the relays I can find @ Parts America.com vs the hayden relays on Willie's write up? Is it just the advantage to have dual fans each going off at different temps?? WIth stock replacement relays, both will go off at the same time at the same temp?? Am I right or confused?

I would think some has an idea about this.

Relays are relays, they have nothing to do with activation temps.

The purpose of a relay is to isolate your switching device from large current sources -- think of it as a "remote switch".

Most automotive relays are single pole, double throw (SPDT) which means that there is a normally-open, and a normally-closed side, in addition to the control terminal. As far as the SPDT automotive relays go, usually the differences revolve around the current rating, and whether or not they are waterproof or not.

HTH,

If you are talking about just the relay, then any relay of the same power rating will do. But the Hayden kit is more than just a relay, it also includes the temp sensors to trigger the relays.
In a stock configuration, the fans are controlled by seperate relays with different triggers. If you rewire them, they can go on and off together.