New vacuum pump differences?

[2.5Turbo]

I'm getting ready to replace my old style vacuum pump on my 300D and the vacuum pump page on the EPC made me ask...what's the difference between the two pumps listed (000 230 31 65 and 000 340 35 65)? The former says "as of engine number 016513" and the latter says "up to engine number 016512". I know what my engine number is and which one I should order, but what is the difference?

Searching the part number at ******** brings up a Pierburg pump without gasket for the 3165 number and a Hella pump with a dam gasket pictured for the 3565 number.