I've got a 9.5" 2700 stall non locking converter, and to keep it cool I have a deep cast aluminum pan and 6AN braided hose running directly to a pair of the 24K GVW B&M coolers (bypassing radiator) bolted back to back with and 800 CFM fan wired to run continuoisly. The coolers are mounted beneath the battery just above the valance.
Even when outside temps are below freezing it doesn't take long for my transmission to warm to about 150 degrees. In the summer it gets up to around 180. Maybe it's just my converter, but I don't think it's possible to over cool the tranny either. The shearing oil in the converter generates enough heat to warm it up quickly in any weather.
David