7.55 can support drive partitions up to 2TBs. It will be really strange though, since the minimum block size will be some obscenely large figure.
SCSI has no practical limit on drive size, unlike IDE.
However, you can't have a single file larger than 2GB on any System below 9.1, and can't use HFS+ on any System below 8.1. Oh, although this is off-topic: You can't use any drive formatted as HFS+ on both an 8.1 and 9.x system. Apple made some changes to the File table and you'll get errors everytime you move the drive back and forth between 8.1 and 9.x. 8.6 and 9.x are ok though.