Google Harborage Marina in St. Pete and Twin Dolphin Marina in Bradenton.
Unless it's located off site, Twin Dolphin doesn't have a yard -- it is a good marina though. Likelwise, Regatta Point right across the river is a good marina but lacks a haul out yard if memory serves.
There are several marinas with yards in the St Pete area.
Looking a little further down the coast may also be a good idea. Burnt Store in Punta Gorda is a little steep (and a little out in the boonies), but may fit your requirements.
Take some time and browse this website: Active Captain
. It's a good tool for marina searches.