Bonnet flutes/louvres.
We have a series 1 and 20 odd years ago I decided that allowing heat to escape through bonnet flutes might work but our daughter forbade me from desecrating the car. So bought a series 2 bonnet (couldn't get a 1) and had louvres cut in it, to my pattern which included a little scoop in front of the air cleaner intake to allow cooler air in, by a gentleman trading as Tin West in Melbourne. That required it to be totally stripped of paint first. Initially ran it as a summer bonnet in unpainted form, then had it powder coated and later stripped and painted.
It certainly has the engine running cooler on the temp gauge, possibly too cool. When you stop after a run you can feel the heat pouring out through the vents as well.
HOWEVER this did nothing to stop the build up of heat in the firewall and cabin that occurs when you park for half an hour and then get back in.
Our car does not have AC.
Have contemplated ceramic coating the exhaust manifolds, which is not that expensive, but the issue appears to be that it just moves the heat from the engine bay to under the body so make that standing heatsink even worse.
Not sure this answers your question!