Most compressed archives can be simple converted from one to another, when he original one is decompressed and the content is compressed again in your preferred format. In case of split multi-volume archives you first need to gather all the pieces before you decompress them.
Convert Split Multi-volume ARJ compressed file archive (part 5) to Compressed file from a multi-volume archive (part 8).
We found 2 software records in the database related to .a03 to .008 file format conversion.
Microsoft Windows software - convert a03 to 008 on Windows
Popular open source file archiver with a high compression ratio
Convert from a03 file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned a03 to 008. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
One of the oldest and most popular shareware file archiver and data compression utility