For a second NIC, you could find one of the SCSI-to-Ethernet converters. One internal NIC, one external.

For hard drives, you could find an IDE-to-SCSI converter. Let you use a large IDE drive on the old internal SCSI interface. Can go very large that way. As long as the converter supports large LBA, it should handle up to the largest IDE drive made. (750 GB is the largest I've seen. Bigger than that appears to be Serial ATA-only.)