I'll assume it has the 1/2 NPT size oil pickup boss and not the standard passenger car production size 3/8 NPT pickup, if so then it may have been intended for use in the 1962 Max Wedge warreenty program. That late in the year casting date it may have even been intended to be used as a street 426 block instead of a M.W. motor This is one of ty]he many reasons I've learn to never say the factory did anything out of the ordinary, especially on our beloved Mopars
As far as boring it out have the block sonic tested by a good shop before deciding I've had two 413 industrial blocks sonic tested and bore out to the standard 426 4.250 bore size, no problems on the sonic tests BTW, there are more than three 426 wedge block casting numbers