Putting an STi bottom end on WRX heads is a much more desirable choice, it makes the swap easier. Search hybrid block on here. You could continue to run your 5 speed either way, you just need a WRX clutch between them.
355 awhp fp green six speed wagon in Corvette Atomic Orange
Well the problem is I have blown engine the top and bottom are no good so I need a whole engine and I want 2 upgrade to 2.5 sti engine and I found 2007 one for good price so dats y I am asking the questions and only thing I am really worring bout is if I am going need the transmision but chase it doesn't matter and from ### has been posted it going be diffcult swap but needs 2 be done
You can't drop an 07 sti motor into a wrx with a ton of work. Harnesses, pedals, ecu, are just a few of the things needed. I think you have swap the motor harness and the body harness to get the STI ECU to work.
Buy the STI motor, sell the heads, get wrx heads. This would make life a lot easier.