Sheets of the FL citrus advertising stamps show up with some regularity on the market, whether retail or auction. Blocks of 4 maybe less so. In fact, Eric Jackson has a sheet of the 2c (FL CFA 15) in his current auction.
I buy state revenues with some regularity, especially through
ebay. I see a lot of material, common and not, go through there. I don't presume to tell anyone how to run his business, but I've seen good results with state revenue material that was started at a low bid and let the market determine the value. It's such an esoteric corner of revenue collecting that even the values in the SRS catalog sometimes miss the mark (for good or bad!).
Best of luck, SPP. Those are some cool stamps.