I did a search but have a couple of specific questions.

Is 1.5 gal a/f with the rest water okay? (California car)
Is MB coolant necessary on the old iron engine?
I will not be removing the thermostat to do this flush, can I get most of it out draining the radiator and the block?

Thanks

BTW, 1974 450SE W116

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63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6