The only overheating problem I've experienced or seen is the fuel pump.
It needs to have airflow from the fan via a hole in the cowling/duct.
Otherwise all ok.
Generally road speeds on Raid are low, sometimes very low, and we tootle along at low revs in third gear. So engine heat output is not significant.
Raid is not a race for highly tuned race cars. It's an extended picnic in the bush.
The much greater issue is how to keep the beer cold!
We did drive flat out for 3 very long days, and caught them at dawn on Raid day 2.
Looking back we were lucky to not have any breakdowns, given that one of the cars was on the road for the first time in over 30 years, and had several dozen homemade bits in it !
Certainly, after that shakedown, the rest of the Raid was like a stroll in the park