CONFIG_CLASSIC32 is not available for thedefaultarchitecture x86.
Result is shown for architecture powerpc

52xx/6xx/7xx/74xx

configname: CONFIG_CLASSIC32

Processor Type
└─>52xx/6xx/7xx/74xx
In linux kernel since version 2.6.16 (release Date: 2006-03-19)  
There are four families of PowerPC chips supported. The more common
types (601, 603, 604, 740, 750, 7400), the Motorola embedded
versions (821, 823, 850, 855, 860, 52xx, 82xx, 83xx), the AMCC
embedded versions (403 and 405) and the high end 64 bit Power
processors (POWER 3, POWER4, and IBM PPC970 also known as G5).

This option is the catch-all for 6xx types, including some of the
embedded versions. Unless there is see an option for the specific
chip family you are using, you want this option.

You do not want this if you are building a kernel for a 64 bit
IBM RS/6000 or an Apple G5, choose 6xx.

If unsure, select this option

Note that the kernel runs in 32-bit mode even on 64-bit chips.