A couple more drives that work with the Vulcan 40:
    MANUFACTURER    UNFORMAT WTH. PL CYLS ST CYLS INTERFACE  ACC  XFER.
POWER
    MODEL NUMBER    FORMATED HGT. HD PREC AC HDS  REC.METH   T-T  CACHE
MTBF
                                     L.Z.    ST        ADDITIONAL COMMENTS
    ------------------------------------------------------------------------
---
    MAXTOR COLORADO   51.3MB 3.50  2  745 28      IDE(AT)   28ms   8.0Mb
8.0W
    8051A             42.7MB HALF  4      VC      (2,7)RLL  8.0ms  32KB
150K
                                     AUTO                             3,484
RPM
    ------------------------------------------------------------------------
---
    QUANTUM                  3.50  2  834 28  965 IDE(AT)   19ms
9.0W
    ProDrv-40AT       42.0MB HALF  3      VC   5  (2,7)RLL  6.0ms  64KB
50K
                                     AUTO     17
MZR:8-ZONE
    ------------------------------------------------------------------------
---

The Maxtor is identical to the Miniscribe MS8051A  that Wayne found to work.

The Quantum has 5 heads, so apparently the Vulcan 40 can work with more than
4 heads, but chokes on 8.  The Quantum is an IDE version of the 3.5" 1/2
height 40 meg SCSI drives that were commonly used in Mac SE's, SE/30's, etc.
It has the fastest seek time of all the drives I've found to work.

Once again, before you can use a drive that came from a PC, erase the
partition info with WipeDrv.exe, a free demo from
http://www.whitecanyon.com/cleandrivedemo.exe or similar. Then connect to
your Vulcan and run the Vulcan Partition.Manager Utility. Say yes when it
asks if you want to create a partition, and when it asks if you want to scan
for bad blocks. Then select format, and format each partition.
-Paul