I have a 1981 380SL and swapped a 500 SEC engine into it. Still trying to work the bugs out of it but it keeps overheating. Here in L.A. it's been hot and traffic is bad. I can drive it for 30 to 45 minutes and the temp slowly creeps up. Once it gets to 120, it wants to stay there. The water pump and thermostat are from the 380. They're both about 3 or 4 years old but only have a few hundred miles on them and worked fine in the other engine. New radiator cap and expansion tank. I'm going to look into getting a bigger core for the radiator tomorrow but wanted to know if anyone knows of other radiators that would fit and solve my problem.