Unless the files have been altered in some way, they should normally work regardless of release versus c-build status.
A regular build from AOS off the support looks like:
ArubaOS_MMC_6.1.3.5_35523
(firmware type, device, firmware version, firmware build)
Whereas a c-build might look like:
C_ArubaOS_MMC_6.1.3.5_99999 (not a real build, just an example)
The key is to not strip the filename of the build number when importing the firmware into AMP.