Having now driven the AJP between clutch issues, I have to agree that any substitute engine will be a positive if it keeps a Cerbera on the road. The AJP is a wonderful engine though
On the radiator question, my Cerb has AC and I think the standard 4.5 radiator, during the summer it did not struggle to keep my LS7 cool with fans only really comming on in stop star traffic, temps were always rock solid (as measured by the ECU)