The only changes seem to be on the kickstart, the workbench is 3.1 with the Magic Pack (Organiser, ScalaMM, Wordworth, etc).
The kickstart rom seems to be a simple 3.1, 1MB size with the following changes:
exec.library 43.4 (10.3.96)
scsi.device 40.20 (18.2.94)
expansion.library 43.2 (10.3.96)
strap 43.1 (8.3.96)
Worth adding to your BB4 installer?