hi i have a 1998 wrx import how hard is it to fit a 2.5 bottom end what would i need to do and change would my heads fit and manifold any help would be gratefull

 

All your original parts will fit the block. You'll need to work out the compression ratio. You'll need aftermarket management to be able to set it up properly. Take a good long look at the 2.1 stroker option, built into your original block, which can be a better choice for a whole lot of good reasons.

 

thanks for the help mate would a ecu from the car that the block is coming from work for now just to get it running till i can save up some more funds to get a uprated ecu and get it mapped

 

Yes, your current set up will be plenty good enough for running it in.