STI5300

iTrader: (4)

I think I have a issue hence the above question. I have a 2.5 engine in my 05 WRX and currently looking for a head gasket set. Are all the blocks the same as mine has 161516 on the drivers side block and 147181 marked on the passenger side block. Should these be the same or do I have a block built with 2 different halves.