You would use either the ASKDEVICE tag or the named device tag. As you can see in my screenshot I'm using the ASKDEVICE, and it's polling everything. Even my RapidRoad USB interface (and all it's associated options) shows up.
So if you wanted to try the named device option, you'd change it to:
(ASKDEVICE)
SCSI_DEVICE_NAME=gvpscsi.device
(no paranthesis on the second line)
Then it should scan just that particular device.
Pretty certain that the .device for GVP controllers is stored in the ROM, so it should be loaded at bootup. Try this: run SysInfo (latest version 4.0 can be downloaded here:
http://sysinfo.d0.se/ ) and scroll through till you see your list of installed expansions or devices. Are you seeing a gvpscsi.device at all (when you're booted up in 3.9)?
No worries man, I took a nearly 10-year break from owning any Amiga hardware, it it all came back to me "fairly" fast, LOL.

As a last thought, when you run HDToolbox your motherboard controller shows up at least, right? (will probably be named scsi.device even though it's technically IDE).
