LOL, I know why/when the RR is often recommended. The 6.0L fuel rails are about 10mm in diameter. The lines to it are the restriction and the fittings the most.
>Not that I particularly want to get into the details, as I said I am choosing to be too lazy to do so, but if excess coolant flow is taken through the heads to a back port that is added, then the question should be - what does that do to the flow of coolant through other areas of the engine. Water pump flow is a relatively fixed component. That said, if my heads were off, I would have the ports installed.
I agree, and there is no way for us to really determine that unless we had the resources of a cooling engineer working on the engine. One argument is it provides more coolant to flow up through the gasket orifices, which I don't see as a major point due to the size of the orifices. Some say it slows the flow rate, so the coolant has more time to accept the heat transfer, which I find to be a poor understanding.
For the 6.4L, INT altered the water pump, added restrictions to the front of the block, and greatly increased the size of the orifices of the 6.4L gaskets, so that is a major change in total. Plus, the head's water jackets are different.
The 6.0L diversion kits still have restrictions within the fittings, no matter the hose size. But the modification will still divert some of the flow through the heads, slowing the flow-through rate. Much depends on when or if the engineers considered nucleate boiling as part of the strategy.
I chose to minimize the flow out of the back of the heads, to not alter much of the coolant flow through the heads.