^ What he said. Find yourself a 32MB module before you do anything. It takes the plain vanilla 72-pin kind so it should be pretty easy to source one of these chips. Apparently you can use bigger ones in there too although 36MB should be more than adequate unless you're running some heavy duty stuff.
The RAM disk will be interesting if you don't have a hard drive. I'm assuming you'll be using a RAM Disk program similar to RAMDisk+, a shareware program by Roger D. Bates which could switch your boot volume to the RAM disk upon startup. The only trouble is that the 475 needs System 7.1 at minimum. It's possible to get a decent System 6 setup even on an 800K disk, but System 7 is VERY tight on a high density disk. You'll also need an enabler for a 475, which takes up a little bit of disk space (every kilobyte counts). You're going to be very limited in terms of fonts, control panels, or extensions; printer drivers are another thing to consider unless you want to put them on a separate disk and copy them over to the RAM disk (you'd have to do the same with the Chooser and any other DAs since you'll likely want to reserve the floppy space for fonts, especially since 7.x doesn't come with any serif typefaces built in).
It may be worth sourcing an external SCSI Zip100 drive to use as a boot disk. Even if you load the system to a RAM disk, this will allow you to load larger programs and get a better system software installation than floppies would.
The RAM disk will be interesting if you don't have a hard drive. I'm assuming you'll be using a RAM Disk program similar to RAMDisk+, a shareware program by Roger D. Bates which could switch your boot volume to the RAM disk upon startup. The only trouble is that the 475 needs System 7.1 at minimum. It's possible to get a decent System 6 setup even on an 800K disk, but System 7 is VERY tight on a high density disk. You'll also need an enabler for a 475, which takes up a little bit of disk space (every kilobyte counts). You're going to be very limited in terms of fonts, control panels, or extensions; printer drivers are another thing to consider unless you want to put them on a separate disk and copy them over to the RAM disk (you'd have to do the same with the Chooser and any other DAs since you'll likely want to reserve the floppy space for fonts, especially since 7.x doesn't come with any serif typefaces built in).
It may be worth sourcing an external SCSI Zip100 drive to use as a boot disk. Even if you load the system to a RAM disk, this will allow you to load larger programs and get a better system software installation than floppies would.