My Rover ran with a two core radiator up until 2005, having covered around 194,000 Miles (312,000km) at that point. Temp would creep up during warm weather, i.e over 30 degrees C when out on the highway, the needle usually sitting just past the '5'. In slow moving traffic, much higher, at the top of the green. My Rover has no air con, so the temp would have been made worse had it been in place.
A 3 core radiator won't cure the problem though, but it does provide more in reserve. Having to run the 10.5 : 1 engine at TDC, which is extremely inefficient I feel is a major contributor to the overheating problem.
Ron.
