Solaris 2.3 and SunOS 4.1.3_U1 tar and dd

I am having difficulty reading 8mm 5GB Exabyte tapes. The tape drive is attached to a SunOS 4.1.3_U1 machine, and I am using tar. The tape, however, contains Informix Online for Solaris 2.3. Normally, I would have the drive attached to a Solaris machine and extract the files with "tar xvfb <devicename> 20". However, I need the tape drive to stay on the 4.1.3 machine. I wanted to extract the files and move them to the 2.3 machine. Informix Tech Support thought I should be able to use dd to read the tape. This gives me "dd: read: invalid arguement" errors. tar insists the blocksize is 10, and give directory checksum errors, to boot. When told to use 10 as the block size, and to ignore directory checksum errors, it STILL fails. Sun believed tar would work if only I could be sure the tape was created by a Solaris 2.3 machine. If, however, Informix used something else to write the tape, they may have only tested extracting it on Solaris 2.3, not SunOS 4.1.3. Basically, does anyone else have a similar situation? The SunSolve cd-rom indicates dd may not compatible between various versions of SunOS, but tar should work. Others have told me dd should work no matter what. Is my only solution to unplug that drive and carry it over to the Solaris machine? Thank you for any help! :) Marc Missire