Here's a convoluted answer to tide you over until someone with a real brain comes along -

The 190D OM621 started life with pump p/n 115 200 12 20. Subsequent versions of the OM621 used the same pump and were upgradeable to pumps shared with the early OM615 (115 220D). Remarkably, the OM615 and OM616 (through the 1980 123 240D) began life with their own pumps but eventually were upgradeable to the 110 200 17 20. By the transitive properly of equality, I'd say you can use a 123 200D pump in a ponton 190D and vice versa but the 123 200D isn't in the US EPC for me to be more sure.

Sixto
95 S420
87 300SDL