Just checked the drawings . I went from an HBW100 (now ZF10M), which has a drop of 62mm, to a PRM120, which (like its current successor the PRM125) has a drop of 72mm. That could have been just about taken up on the mounts, but the engine would have been waggling about right at the top of the threads, so the mounts were packed up at the bottom on steel blocks.
However, the OP has an HBW125 (superseded by the ZF12M) which does indeed also have a drop of 72mm. However the lengths are different, the PRM120 is 26mm longer, mounting face to flange, so the OP would need room for that.