Why not have a diesel injection shop repair the dault on your IP? Usually it is a simple repair, and if it looks like nore than that, they will be able to advise you on the compatability of the second pump. If you do need to use the old pump it would be a real disappointment if it were installed and then other problems cam to light. In any case, it would be advisable to have the IP overhauled before installing it.
Just my opinion.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.