Hello all, just adding the bit I have learnt about the cooling of all Mopar Big Blocks over the years in the Heat here in OZ, I have found that the Major cause in most cases of over heating is because the core of the Radiator is blocked with rust scale, the Big Block Mopars seem to always have it even if the Block has been acid dipped and flushed. I have found that the easy solution is the so called SOCK that fits into the upper tank and is held in place buy the top hose, it looks to be made from some sort of nylon, it is a tough heat proof gause that catches any scale and stops it blocking the core, very simple but it works a treat. Of course you do need to keep the original Steel Fan, basicly the more Blades the better, and a good Fan shround is a real bonus, makes all the air from the fan be drawn through the radiator instead of going around the side, so there you have it, aside from things like leaking head gaskets and rotted fins on the radiator and no thermastate I have found the above to be the main heating causes inBig Blocks, regards George.