Allan, that's probably well beyond the scope and knowledge of most Realtors, although there are probably some that are both builders and Realtors. Some one who may be able to help you is:
Jon is a custom home builder who blogs frequently here on Trulia. You might also just google "home builders" in Palm Harbor and call a few to get better ideas. They will probably charge you a fee for an estimate of costs, if you have original blueprints it would make the estimating simpler. Good luck!