James Wetterau says:
> 
> This seems like it ought to be simple but I'm stuck.  
...> 
> fdc1 at pnpbios0 index 21 (PNP0700)
> fdc1: io 3f0-3f5 3f7, irq 6, dma 2
...

Whoops, nevermind!  I needed:
fd*     at fdc? drive ?                 # the drives themselves

and needed to pull out:
#fd0    at fdc0 drive 0

which was valid on a different machine.

All is now well.