Right antifreeze/coolant type for 67 LeSabre?


I'd like to change the coolant of my 67 LeSabre with 340cui engine. because it shows a bit of "rust colored flakes" swimming in the radiator. Over that I have a small leak at or around the thermostat housing which will surely lead to coolant loss during repair.

So what to use as coolant? Right now my car has a greenish/yellow type of coolant - I bought the car in 2021 and never changed/refilled the coolant since then so I'm not sure, what coolant type this might be. The PO imported the car from Canada, so the coolant might be filled in there or in the US.

Here in germany yellow cooland is quite uncommon - most cars got either red/pink or blue/cyan coolant. And they always tell you "don't mix the colors". I
just checked rockauto.com, they offer several different types for my car/engine in different colors (green or yellow), all not available over here and shipping them would be quite expensive:

FVP GREEN5050GAL (green, IAT, low silicate)
PRESTONE AF3300 (green, IAT, low silicate)
VALVOLINE 719009 (yellow)
FVP DEX5050GAL (orange, OAT)
VALVOLINE ZX001 (yellow, low silicate)
PRESTONE AF2100 (yellow, Ethylene glycol, phosphate free. OAT)

Is there a "formula description" or technical hints what to chose best for coolant? I know the 340cui engine is entirely made from cast iron so you don't have to think about stuff that protects aluminum engine parts.

Any help appreciated :)

I find anti-freeze a challenging topic too. For the old cars, I choose anti-freeze suitable for diesel engines. "Low Silicate" or no silicate is good.
I have been considering "Preston heavy duty anti-freeze" (because of availability), CLICK HERE!

I don't worry about aluminum radiators, I believe the requirement for "Aluminum Compatible" anti-freeze comes from the high heat around aluminum heads and block. Maybe somebody who knows will shoot me down:)