do you think this would work as a less expensive oil cooler?
 

I was reading an old "Hot Rodder" mag about mods under $50. one of them was to use a large ato tranmission oil cooler. the price was about $40 i think. They said it doen't reduse the pressure very much at all because auto tranmissions can't handle it.
what do you guys think?

No. The best and the only oil-cooler you should use on your '7 is the stock one, unless you add another cooler as a SUPPLEMENTARY cooler. Those tranny coolers are shit, even Mazdatrix agrees with me. :)

okay. all I wanted to know
but why are they using them on the 8s with 300+ horsies?

Because the oil-cooling demands of an 8 is not nearly as high as a rotary. A rotary is cooled primarily by oil and the stock system does a fine job. As far as I know, the stock coolers work the best for this job...I could be terribly wrong, but I think that most of the hi-po guys on here are using the stock cooler.

I used an oversized tranny cooler on my old RA64 Celica back in the early 80's.

The biggest problem was that it kept blowing out or blowing hoses. The auto tranny coolers must run on considerably less pressure than the oil system.