I can't speak for the SE machine but I do have a SE/30 with a 8GB SCSI drive plucked from an old server. The drive has a SCA connector so I have to use a SCA to HD50 adapter. SCSI is very good at being backwards compatible, as long as you make sure to have proper termination (I got an adapter with active termination rather than the cheapest route).

Mind you, I only have a 2GB partition on it, but I've used the other space to experiment with A/UX (Apple Unix) dual-boot environment.

Edit: Oh, and if you use a non-apple drive you probably have to modify the front HDD Activity LED-connector a wee bit. I had to extend the cables on mine to be able to connect it to the adapter.