The -500 where touted for a range which it initially didn't make, the early aircraft went back to Lockheeds and 4.5 feet where added to each wing along with longer, active ailerons and uprated engines (524B4 as an option), which was what the 6 BA aircraft got, they also came back with other modifications such as RSB.
The -100/-200 had a single cell in the centre wing box for fuel, and the -500 had 3 cells for fuel, so your statement about them having the same range is incorrrect.
As to the -250, not having worked on them I do not know there cell set up or range.
