The difference between the B and B1 is only the data plate, this was done for CDN operators for the aboved mentioned licensing requirements. The Difference between the original A's are considerably different from the B's. Starting up top with metal blades vers fiberglass on the B's thus increasing the gross internal weight limits. There have been many other mods that help the performance and maintenance. The B's are a great machine, yes they to require the odd band ajustment pending on Alt & temp variations on the job, but not many at all. The overhauls ie GP wheel shimming is critical for both fuel burn and efficiency ....... this can cause problems during power changes ie. popping. With 3000 hrs on the B's and 8 other endorsements she is still my favorite and probably will be till the day I TX. Your aircrew is what makes or BREAKS this aircraft, cowboys can hurt her fast!!