[cctalk] Finding tar block size.

Trying to tar a directory and transfer it to my AT&T 7300 (SVR2 unix). Tar -tf works fine on the Mac OSX, but when I copy it over the Unix (not gnu) tar gives me a: Tar: blocksize = 20 directory checksum error When I try to tar -tf the file. Which usually means the block size is off. Any way I can check to see what the block size is on a modern system (like a Mac)? tar -tvf doesn't seem to tell me. Thanks! C