First let me say Doug that you have 3 very nice vehicles. Second I am not familiar with the fluids that you use for your Ford Diesel, but I would ask you this, are those expensive? A little 300 SD ain't heavy duty so although it may be compatible, why spend the extra $$$ when you won't get anything much in return. Unless you are buying this in bulk, I would stick with the non-heavy duty stuff for the 300.
Regular coolant at the supermarket will do, just make sure you have 50-50 mixture. Oil weights I would refer to your manual. YOu can never go wrong with a 10W-30 or 10W-40, and / or 20W-50 if its hot weather and you're burnin a little oil.
This may not have answered your question, but my 2 cents anyway. You don't have to over kill the 300.
'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)