FreeArc archives (.arc) can be repacked to any other file archive format that is supported by FreeArc itself that supposedly include .ark files. You can download it for free, so should be pretty easy to achieve arc to ark conversion should you need it.
Convert FreeArc compressed archive to ARC File Archiver CPM/Port archive.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert arc to ark on Windows
A multi-platform archiving application
Convert from arc file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.