All models are the same toilet. The only difference is the toilet with the D has and insulated tank, the toilet with a B has a bolted down tank lid. The model with both a D and B has both and the model without will not have either feature.
The Carusoe CST716 toilet has a 2" flush valve and has a gravity feed flush. The Drake CST744S has a 3" flush valve and is a G-MAX flush.