there are only a few choices for AEM rods for d15 blocks. tell him to swap to a d16 block, if he really wants to build the internals. otherwise, you need a JDM D15B crank (it has the correct main journal sizes for the d15 block) to run the d16 rods.
OK, I see you're in Germany so I'm going to give you the European lowdown on this : it is impossible.
The JDM (="japanese domestic market") D15B was a 1.5 litre variant of our ESi (D16z6) engine with a 3-stage Vtec mechanism. It was never imported into Europe.
The rod bearings on a D16 are 48mm, on any D15 you can get your hands on they are 45mm so the rods will not fit. They are also a different length I believe because the D15 block is slightly less high than the D16 block. Cilinder heads are the same, so your friend is best to get a D16 SOHC (NOT from a DOHC D16 like the a8, a9 and z5 ! I know they are plentiful in our regions, but they are useless to him). The engine codes to look out for are : D16a6, a7, z1, z2, z6,y7, y8. You can find them in just about every 1.6 litre sohc Civic or Concerto except the 88-91 Civic 1.6i-16 and the 88-95 Concerto 1.6i-16. The Rover 216 GSi or 416 GSi is also a valid donor.
He can build up that block, and use it with his current cilinder head. Naked D16 blocks are dead cheap, I wouldn't pay more than €150-200 for a good one (maybe €500 for a complete and sane ESi engine including the head !).