I checked the original 28 instruction book it says to flush out the trans and rear with kerosene,doesn't mention the engine,just change the oil every 500 miles
I am not dropping the pan again.
I just did it twice.
Once before I started my engine.
And again after I replaced the timing wheel.
I will not drop the pan again for another 20 years! or maybe never.
I was just asking about original engine service ..oil changes etc