I've had SCSI <-> ST506/412.
Do you know a source for a SCSI <-> SA400/800 ?
SMS OMTI 5200 (412 + floppy)
SMS OMTI 5400 (412 + QIC02 + floppy)
OMTI_5x00.pdf under sms on bitsavers
They have a NEC 765 floppy controller on them.
also (not on bitsavers yet)
OMTI 7000 series