If you're going 200 mph and your engine is putting out its rated power then yes, the torque converter clutch isn't going to be sufficient.

BUT............................
At 60mph you're using about 35 horsepower and no matter what engine is on the front, the torque converter clutch only has to transmit the torque to make that horsepower at the cruise rpm.

My 4L80E in a 3/4 ton suburban never had been out of the truck (no internal repairs) when I parked it at 253,000 miles, and a lot of those miles were in city driving. They are pretty strong. It was a front seal leak that I didn't want to fix that got it.

R.