musicistabest,
You'd need a power supply compatible with the drives you are using a well as external/internal connectors compatible with the drive types you're using (i.e. SATA, EIDE or SCSI).
I guess I'm curious as to WHY you'd want to build your own when you can purchase external enclosures with drive bays, power supplies and internal/external connectors.
Check out:
http://www.newegg.com/Store/SubCateg...nal-Enclosures
Hope this helps.
- John