Fun to watch. 200kph (124 mph) in an old Mustang is more of a white-knuckler than 300kph (186 mph) in just about any new car.
I've driven on the autobahns many times, and my biggest concern in that Mustang would be not having anywhere good enough of brakes to get yourself out of trouble, should the traffic ahead suddenly slow down.
The guy has yet to figure out that his turn signals don't self-cancel. Made that left turn onto the autobahn on-ramp with the right turn signal still blinking. Drove that way on the road too.
The car did great, however, and I hope he gave it a nice bath and a pat on the rear fender for taking him out on that early morning and not blowing up/breaking down/overheating or otherwise giving him any trouble.
He should invest in a tach, however. His car probably has 3.00 or taller gears to run that speed, for that long, without the engine coming apart. The engine sounds pretty much stock.