[TUHS] v6tar from v7 on v6, too large?

All, According to "Setting Up Unix - Seventh Edition", by Haley and Ritchie: The best way to convert file systems from 6th edition (V6) to 7th edition (V7) format is to use tar(1). However, a special version of tar must be prepared to run on V6. The document goes on to describe a reasonable method to make v6tar on v7 and copy the binary over to the v6 system. I successfully built the v6tar binary, which will execute in the v7 environment. I then moved it over to the v6 system and did a byte compare on the file using od to dump the octal bytes and then comparing them to the v7 version. The match was perfect. The problem is this, when I attempt to execute the v6tar binary on the v6 system (it works in v7) it errors out: v6tar v6tar: too large on the v7 system, it works: v6tar tar: usage tar -{txru}[cvfblm] [tapefile] [blocksize] file1 file2... I don't think the binary is too large, is is only 18148 bytes. ls -l v6tar -rwxrwxrwx 1 root 18148 Oct 10 14:09 v6tar Help. First, what does too large mean? Second, does this sound familiar to anyone? etc. Thanks, Will