I use the Prestone pre-mixed 5
I use the Prestone pre-mixed 50/50 coolant.
The right way to flush the 348 system is to drain the system at each radiator, left and right side, remove your thermostat and plug the bypass hole that is underneath the normal thermostat location, and then pressurize water through your coolant fill cap opening until no more brown radiator rust comes out anywhere...
Then drain the water and refill with Prestone pre-mixed 50/50 green coolant.
And of course, remember to unblock the engine coolant bypass underneath your thermostat.
Now, with your ignition key turned to Run (not Start), set your heater to max high while you bleed your system (you'll just put a wrench to loosen the bleed screws on the right side of your engine bay on the black coolant pipes).
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OK, some car owners install coolant filters at this point. You might consider doing the same (less debris hitting your waterpump blades).
Some race-car shops also replace their solid black rubber coolant hoses with transparent FEP Fluoropolymer coolant hoses...this lets you see air bubbles so that you know where your hot spots are located and when it is time to bleed your cooling system...and it helps you spot rust/debris sooner.
Just some thoughts to consider.