Construction numbers of "straight" 200's start with BB-, 200C's start with BL-
We have a fleet of 17 B200's all starting with the serial BB, they all have cargo doors (fitted after market). Most aircraft with larger doors if not already being used for freight, are with aeromedical operators. Have seen some older models for sale in the Australian aviation magazines.
Older is probably better for freight as the empty weights are lower, the newer Kingairs seem to be a lot heavier...