h20bob, welcome to the h23 and to this forum. Check for the type of mast you have (three different makes were used as original equipment on the h23) and then go to the manufacture's site to see what it looks like. Among the basic designs: an aluminum block the mast fits over, and variations on a plate with sides that a bolt goes through to provide a pivot for the mast base and pin it to the tabernacle.
Make sure to get help in raising the mast and tuning the rigging the first time. Its not terribly difficult, but knowledge and experience makes it easier. Good luck and have fun.
Jim Kolstoe, h23 Kara's Boo