40"4"= 3:23 gear ratio
40"8"= sure grip
Neither indicate size of ring gear.
To know which rear was installed at the factory, check "axle" under the build code section of a build sheet. For my 66 with 3:23 sure grip, the build code is 011 and it is a 7 1/4" rear. Someone with a factory 8 3/4" A body car, please post that number.
