Bypass Radiator Cooler - URGENT

[sd1800]

Need to know people's opinions. Car is currently at Auto shop and I need an answer for him by tomorrow morning.

Torque converter is rooted & forward clutch has worn (115,000km) due to previous owner towing a boat to Port Macq with no cooler. I want a external cooler fitted also for peace of mind for the future.

Does everyone here recommend that you bypass the radiator completely when using a external cooler, or do you use it in series? I wanted it bypassed, but he said when sitting in bumper to bumper traffic if you are not using the radiator cooler the trans will heat up real quick because it isn't getting any flow from the Thermo fans. Is this true? Whats the case here?? FYI car is used 90% city driving. He mentioned it's very uncommon for private AU's to experience the coolant>transmission problem. Moreso taxi's.

Also, If i was to ask him to fit a higher stall, what rpm would be suitable for a daily driver on the street?

Thanks in advance.