As Ganguli himself explains in the preface to his translation, he used two different editions of the Mahābhārata text, namely, Bengal and Bombay:
I cannot lay claim to infallibility. There are verses in the Mahabharata that are exceedingly difficult to construe. I have derived much aid from the great commentator Nilakantha. I know that Nilakantha's authority is not incapable of being challenged. But when it is remembered that the interpretations given by Nilakantha came down to him from preceptors of olden days, one should think twice before rejecting Nilakantha as a guide.
About the readings I have adopted, I should say that as regards the first half of the work, I have generally adhered to the Bengal texts; as regards the latter half, to the printed Bombay edition.
Sometimes individual sections, as occurring in the Bengal editions, differ widely, in respect of the order of the verses, from the corresponding ones in the Bombay edition. In such cases I have adhered to the Bengal texts, convinced that the sequence of ideas has been better preserved in the Bengal editions than the Bombay one.