I have had the same result with the Black Magic fan since '98. I haven't had to replace anything yet, but then again the fan runs all the time so it is basically fool proof. With headers, the A/C on full blast, and 100* yesterday the temp never rose at all. The Black Magic is rated to 220ho with A/C, so it should work for the 3.0 auto.

Do you have all three cooler units together?, if so you might think about relocating the tranny cooler, or adding an additional cooler with fan somewhere else.

I thought the Runners came with a small pusher fan in front of the radiator already?

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed