If we assume that the Bandai dimesions are correct, then the Revell kit, at 250mm in length gives a scale of 1:48.96 (aka 1/49) So 1/50 scale might be considered a simplification by Revell. However, being 1/49th scale makes it more compatible with the Bandai 1/48 scale T-65 kit, from a "constant scale collection" standpoint. I am glad to accept this minor discrepancy for the sake of not having to hack apart a Revell T-70 in order to 'upscale' it slightly as my OCD was telling me to do! ;^P
I'd say, just perhaps double the dimensions and call it a day!
Regards, Robert