Do you mean [url=http://www.sunshack.org/data/sh/2.1/infoserver.central/data/syshbk/Devices /Communication/COMM_SPC_S.html]THIS[/url] very old SBUS card ?
The installation manual can be found at Docs.Sun.Com
http://docs.sun.com/app/docs?q=800-5246
It is so old a device that I think that the manual is all you will ever find online.
It has been a very long time since that card was sold or supported.
The online manual states in Chapter #3 that the driver software
was in the shipping box, ON A FLOPPY DISK,
unless you paid extra for it to be shipped with the software on an optional tape cartridge.
Drivers were included in Solaris 2.3 and newer, so there was no need to maintain separate driver file.
There were never any freely downloadable files for Solaris 1.x(SunOS 4.x)-- ever.
The card, itself, was EOSL so very long ago.
Newer versions of Solaris would recognize it natively.
Unless you use a newer Solaris, I fear you are completely out of luck.
That's what I said in my first response:
Unless you just simply erase your Solaris 1.x and install
a newer version of Solaris that recognizes it natively ...
... there is no place to download it.
I can only provide a very wild and crazy suggestion.
Wait for someone to offer to sell it on EBAY.