Neal, I am running B&M's 24,000 GVW trans cooler in both my syclone and S10. Summit part number for it is BMM-70264 at $49.88. B&M has a larger cooler, 28,000 GVW #BMM-70268 at $59.88. However, it doesn't come with hose, barbed fittings or clamps. It is also set up for 1/2" NPT fittings whereas all the other coolers are just barbed. So, if you are on the "braided line" bandwagon, that may have some merit for ya.
Being that you live in Californication, you could very well get away with bypassing the stock in radiator cooler. However, one thing to keep in mind is your trans fluid will take longer to heat up to normal operating temp because it won't be getting heated by the engine coolant that it would be if you were still using the stock in radiator cooler. Keeping with "too much of a good thing" ATF that is too cold can be bad because the seals won't expand and seal properly. Which makes it more likely that they can get damaged if you drive "spirited" with the trans still cold. It's not so different than letting a motor reach normal operating temperature before you go out and beat on it.
Having both coolers in service works out nice for me. My cooling circuit is plumbed so that the ATF goes through the stock in radiator cooler before the aux one. Figured that the in radiator one would remove some of the heat and the aux cooler that is independent of the in radiator one can cool it even more before it goes back to the trans. Retaining the stock cooler also gets the ATF to normal operating temp sooner too. During the cold Ohio winters, I use two cable ties to secure an old license plate turned backwards on the grill of my S10 in front of the cooler. That way my transmission can GET hot. I don't drive my syclone in the winter so, it's not an issue for it. With regards to the trans temp sender here's the set up that I have on my S10:
"Summit remote transmission filter #SUM-G4980 with Autometer trans temp sender and AC Delco PF13 (short) filter that I have on my daily driven 3.4L S10." HTH's
