I don't think where I live counts as tropical but it does count as
really bloody hot. Normal air temperatures can get to be 105-110f and
that's nothing compared to the temperature on the ground on a street
with no shade around.

When I first got my 164 it ran so hot that if you put an ice cube
on the head it would jump around and then vanish without ever becoming
a liquid. The temperature gauge would hover at the center of the range
or higher with the motor on and dive straight into the red. If I sat
still with the car for very long it would similarly start to overheat.

Mine was a 1970 with the single piece intake / exhaust manifold. My
manifold had cracks and was warped and there were some nasty vacuum
leaks and such. I replaced the manifold and had the radiator recored
and I replaced some other stuff like the heater valve that was always
on.

After fixing these issues the car never came near overheating again.

I think the FI cars are even better setup to deal with heat because
I think they've got a better radiator design and the intake manifold
is better at sucking cooler air from the front of the car and not
heating it up like the carb manifold.

So, if I were you, I'd just get everything back to stockish condition
and try to deal with problems if they persist.
chris