[cctalk] Finding tar block size.

[Chris Zach via cctalk]

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