Was your mechanic even alive when the car was built?
I totally agree. I never heard of a well running car overheating due to a carb not putting out enough fuel. Back in the day, I used to drive my '71 Pontiac for around a 600 mile trip.When I drove my 70 Road Runner across country in 2015 we drove sustained speeds of 90+ MPH through Kansas with a top speed of 108 MPH. Our 90+ speeds lasted about 2 hours or so. There is no reason, from a cooling system perspective, that your car shouldn't be able to do the same.
He was born around 1961.Was your mechanic even alive when the car was built?