First, a critical clarification: There is no official "MDK 474" version. This is a common user abbreviation referring to Keil MDK version 5.24a whose internal build number is 474.
This release was a stability-focused update to the MDK 5.2x series, addressing several bugs related to debugging, flash programming, and project management. keil mdk 474 download
Instead of hunting for an obsolete toolchain, consider migrating your legacy project to Keil MDK 5.38 or later. Arm provides a Migration Tool that converts .uvproj and .uvopt files from MDK 4 format. You must still set the compiler to "Use ARM Compiler 5" (not 6) for compatibility. Keil MDK 474 Download: The Complete Guide to Version 5