Not all V8 water pumps are the same quality, even 'back in the day'. I found that impellor size varied, as did the clearance to the water pump body. In the MGBV8 I never had overheating, but there was an un-statted oil cooler (in front of the radiator)!
There as one memorable journey back from Salisbury in August heat where it was so hot that there was a slight drop in oil pressure, and when we got home the windscreen washer water was so hot that I couldn't stand my finger in it!
