Can you put a 2002 WRX engine into a 2000 2.5 RS Impreza?

Answer 1

Yes you can, with a lot of elbow grease and the right tools. Should be pretty straightforward. To add to this, Subaru parts are like legos, so you have tons of leniency in this area.. Seriously, you can grab pretty much anything from any model and bolt it right up to any other model, doesn't even matter what year they are. People build Frankenstein motors all the time, someone will put new 2.5L heads on a 10 year old 2.2L block, run the injectors from a 2.0L WRX, grab the intake manifold off the first Suby they see in the junkyard, swap in the STi pistons their friend was gonna sell after building up his own motor, then blah blah (yeah, I could go all day..)