I was given a bunch of multibus boards many years ago. There were many iSBC 286/10 and iSBC 286/10A boards in the group.
These boards were used in a two-processor i310 machine to provide multiprocessor capability. Under XENIX, they worked very well.
The ROMs appear to be standard Intel boot ROMS. Here they are: U40-135625-001.bin. U75-135626-002.bin.
1238 MST 10 June 2013