I'm not sure Mini vMac supports NuBus computers, check with Mame if you can. My hardware is based on the Macintosh II w/o PMU
I don't think Snow does NuBus either; MAME's the best bet, although QEMU also supports NuBus.
Looks like Mini vMac and Snow both emulate a graphics controller in slot 9 for a Mac II in Infinite Mac.
The problem with my SlotsGrab and SlotsDump on 24-bit Macs is that the Slot Manager returns addresses in the 16 MiB ranges (e.g. 0xF9000000). Translating that address to the 1 MiB range (e.g. 0x00900000) wouldn't help since it appears that the Declaration ROMs of NuBus cards are not memory mapped in the 1 MiB ranges. In that case, the Slot Manager APIs are required to get the data from the 16 MiB ranges. Previously, I was accessing the memory directly. Maybe someone with 68K Mac knowledge or the emulator writers can tell us how the 16 MiB ranges are accessed on a 24-bit Mac? Through some kind of NuBus memory controller? I don't think the supermario GitHub repository includes the code for this.
Anyway, I made some changes to the 24 bit code in my fork. There's a new v1.7 release.
SlotsMem grabs a direct copy of the slot's address range (skips slot 0 because that's not a real slot). On a 24-bit Mac, this is 1 MiB and doesn't include the declaration ROM. For a graphics controller, this should grab the current value of all the registers and the framebuffer. On a 32-bit Mac, the range is 16 MiB and should include the registers, frame-buffer, and declaration ROM.
SlotsDump grabs only the declaration ROM of each slot (including slot 0) and also parses the declaration rom data into a text file.
SlotsGrab just grabs the declaration ROM(s). Use SlotsParse on a modern Mac to parse the declaration ROM file.