Ive got a 2003 subaru baja what subaru motors will fit it

As long as you have a 2.5 SOHC (stage 2) you should be able to use 99-05 2.5 engines. You'll possibly have to swap your intake and components over depending on some differences. You'll also want to note any cylinder head differences / spark plug location. idk if that even matters as far as running goes verses having to swap your cylinder heads over. I posted about this on a recent subaru question: http://www.cargurus.com/Cars/Discussion-c5826_ds667892