Replacing Sherwood water pump with Oberdorfer

[Analgesic]

I think my 1988 C34 has a Universal M-25 engine and at the end of this season I found my 5 year old Sherwood water pump to be leaking and rusting badly.  This came after a stressful impeller replacement that took an hour while under sail after the engine overheated this Summer from a blocked intake.  I'm ready to switch to the front plate Oberdorfer  for cost, convenience and hopefully better longevity.  My current pump is mounted with two hex bolts through flanges into the engine blocks.  I see that the Oberdorfer has 5 mounting holes on the engine block side.  My questions-will the two current engine block holes line up and be adequate to hold the Oberdorfer on or do I have to drill additional holes into the engine block (which frightens me)?  If I have to drill the block, is there anything I need to know having never drilled into steel before?  Any guidance is greatly appreciated.
Brian McPhillips

[Ron Hill]

Brian : Look at your engine and I believe that the 4 holes (the 5th is not used) are already drilled and taped in the front accessary case of your M25XP engine!!