I have a 2001 480 sb which had the same chocks as your picture when we fitted them they were so tight going in we figured that they would never move so we didn't bother with the hold down bolts. Big mistake! now we only have the one and I just can't find who might sell these.
Been in SoCal for decades had sailboats then Ocean Alexander trawler bought Searay 48 sedan bridge (2001) June of this year. Presently in Chula Vista marina that turns out to be surprisingly nice.