Hello,
I have almost same environmet.

| My system is: Macintosh LC 475
| Ram: 20megs
| HD SCSI: No problems there
| OS: Mac OS 8
| 32BIT mode: on

You had better review your booter setting.

| videoaddress was 51901000, now set to f9000000

If your kernel version is 1.4 or newer,
LC475 video address hack option should be off.

| Env: "SERIALCONSOLE" set to 1 (0x1).

If you want to use console on the lc475 video display,
serialconsole option should be off.

Good luck.
--
Ken'ichi Ishizaka