After a few of the cards took an annoyingly long time to arrive I finally have the results for the eight cards I tried (this is going to be a long post, skip to the bottom if you don't feel like reading all the way through):
Card 1: Evergreen Technologies FireLine USB 1.1/Firewire combo card
I had high hopes for this card until I re-read the page on The 6400 Zone that said it wouldn't work because it drew too much power from the PCI bus. Indeed, when I installed the card my TAM refused to boot at all, just freezing at the Happy Mac or right after it started loading extensions.
USB Chipset - CMD 670
Firewire Chipsets - Texas Instruments TSB41LV03/TSB12LV23
PCI Bridge - Intel 21152
Card 2: Sonnet Tango 2.0 USB 2.0/Firewire combo card
I didn't figure this card was going to work, but I picked up one anyway just in the off chance I'd get lucky since both the USB and Firewire chipsets were NEC. No such luck. Even with the Sonnet-provided PCI bridge patch the only thing that showed up in System Profiler was "pci-bridge".
USB Chipset - NEC D720102GC
Firewire Chipset - NEC D72874GC
PCI Bridge - PLX PCI6140-AA33PC
View attachment 11403
Card 3: SIIG JU-2NE012 USB 2.0/Firewire/Ethernet (10/100) combo card
I bought this for a different machine but gave it a shot here. No dice, just showed up as "pci-bridge".
USB Chipset - NEC D720100AGM
Firewire Chipset - Texas Instruments TSB43AB23
Ethernet Chipset - Realtek RTL8139D
PCI Bridge - HiNT HB1-SE33
Card 4: SIIG JU-2NG011
Given that the 10/100 version didn't work I didn't think I'd have any luck with the gigabit version, and I was right. Just showed up as "pci-bridge".
USB Chipset - NEC D720101GJ
Firewire Chipset - Texas Instruments TSB43AB23
Ethernet Chipset - Realtek RTL8169S-32
PCI Bridge - HiNT HB1-SE33
Card 5: Adaptec AUA-3020 Rev A
I was hopeful for this card since Adaptec has made a lot of Mac products. Nothing, just "pci-bridge".
USB Chipset - NEC D720100AGM
Firewire Chipset - Texas Instruments TSB43AB23
PCI Bridge - HiNT HB1-SE33
Card 6: Adaptec AUA-3121
It was out there, figured I'd give it a shot. Same result, "pci-bridge".
USB Chipset - NEC D720100AS1
Firewire Chipsets - Texas Instruments TSB41AB3/TSB12LV26
PCI Bridge - HiNT HB1-SE33
Card 7: Adaptec AUA-3020 Rev C
Maybe a different revision would be better? .Different, but not better. Usually froze on startup, but very occasionally would show up as "pci-bridge" and the Firewire ports would work.
USB Chipset - NEC D720100AGM
Firewire Chipset - Agere FW323-06
PCI Bridge - Pericom PI7C8140A
Card 8: Belkin F5U508 PCI rev 3.0
This card was the best of the bunch. It was off to a good start since it actually showed up as two USB ports and one unknown PCI device (what turned out to be the Firewire part) in System Profiler. Unfortunately only the Firewire side worked. Even though USB showed up, nothing plugged in to either of the ports was ever detected. I have to wonder if this is because it's not getting enough power to drive both the Firewire and the USB ports. If there was a way to piggyback a molex connector off of something else in the machine to run to this perhaps it would fully work.
USB Chipset - ALi M5271
Firewire Chipset - Agere FW803
PCI Bridge - None?
Results:
So after all that, I'm back where I started for the most part. If anyone has a Sonnet Tango 1.0 they'd be interested in parting with I'd love to buy it, or if you would let me know what chipsets/PCI bridge it uses I might luck out and find a generic version. On the flip side, if anyone sees a card in the group above they'd like, let me know. They should all work in Macs besides the 54/55xx, 64/65xx and TAM since they all mentioned Mac compatibility (though most said the B&W G3 was the minimum required).