EJ25 head differences

[sprbxr]

I have a question about EJ25 twin cam heads.

When did the spark plug access holes change? It seems like there is an early head and a late head that require different o rings for the cam covers. Are there any other differences between the heads?

Thanks
Justin

[decke48]

from what i understand is the 96 has different head than the 97-99. and the valve seal kits there are 3. 1) 96 (unknown production dates) 2) 97-98 (production dates 12-1995 to 09-1997) 3) 98-99 (production dates 10-1997 to 05-1999)