Would be like EJ251XX2YY
or something like that
the new one will be EJ20(K,G,7,5) etc See below
Quoted from Scoobynet.com
MY96 STi 2 - EJ20GDW5PR
(change to Phase 1.5 - NO reset of year field)
MY97 STi 3 - EJ20KDW6PR
MY98 STi 4 - EJ20KDW7PR
(change to Phase 2 - reset of year field)
MY99 STi 5 - EJ207DW1PR
MY00 STi 6 - EJ207DW2PR
(change to New Age Bug Eye, NO reset of year field)
MY01 STi 7 - EJ207DW3CR
MY02 STi 7 - EJ207DW4CR
(change to Blob Eye / twin scroll, NO reset of year field)
MY03 STi 8 - EJ207DW5CR
MY04 STi 8 - EJ207DW6CR
MY05 STi 9 - EJ207DW7CR
(change to Hawk Eye, NO reset of year field)
MY06 STi 10 - EJ207DG8CR
MY07 STi 10 - EJ207DG9LE
The EJ205 should follow the same pattern, yes. But note, that EJ207 can also be applied to WRX-RA engines: so an MY99 WRX-RA engine would be EJ207DW1KD or EJ207DW1KE. Also, there is some oddness because you get EJ205DW1KE in MY99 WRX Wagon, it seems the sedan gets an EJ207 designation, which seems odd.