Direct replacement
Unless you want to redrill your mounting block and transom (not to mention close up the existing holes), I recommend you find a direct replacement.  Call Rudy at D&R Marine.  His website is drmarine.com.  He used to work at Oday and knows exactly what will fit.  He got me a replacment motor mount for my Oday 23 that allowed me to simply bolt the new unit to the boat; no re-drilling or filling necessary.  Not the cheapest price for the mount itself (I saw it in the BoatUS and West Marine catalogs for about $20 less), but overall it was definitely less money, as I didn't have to haul the boat, buy epoxy, spend my time, etc, installing a new configuration.  Also, I was happy to pay for Rudy's expertise.