FYI. I was able to successfully upgrade a Seagate ST31000340AS w/SD15 to SD1A using a Wiebetech RTX-200 external enclosure connected to an eSata PCi card in a MacPro 8-core. The ISO disk (CD) identified all my HD's (3 Western Digital, 1 Seagate) that were inside or connected to the MacPro, then allowed me to choose the upgradable HD in the Wiebetech enclosure, allowing a firmware upgrade to that disk only.
Worked like a charm.