FYI:
As it's been said already, the oil jets are non existant in the na engine. Have a look at the pictures below taken from page 45 of my 1982 sales brochure:
The circled area on the left illustrates the oil jet and the piston. The circled area on the right shows where the oil jets are located in the block. The picture below it (b&w) illustrates the na engine. I don't see any oil jets.
Also, from the PP/IMPCO catalog, it seems that the non turbo 300D and the 240D have the same part number for the pistons. If anyone has info from MB to prove that the na engines have oil cooled pistons, please post it, as it would be a learning experience for me and a lot of us.
Regarding the issue of which engine weighs more, page 7 (covering the 300D turbodiesel) of the brochure states:
"The turbodiesel transformation brings a 45 percent power increase, at the cost of less than five percent more vehicle weight."
I can't find anything in there that says the SD and D engines are different. I know the oil filter hosings are different. The crank might be the same in both but the one in the trubo is nitrided for increased hardness and fatiigue strength.