Sweezyboi

Hey all, got myself an 2003 NA subaru impreza GX manual (blobeye), its got an open rear diff, believe its 4.111 (from the minimal open diff info i've found online lol), was wondering what differentials from across the subie years and models i could just straight swap over? looking for some kind of LSD to put in, for street and ultimately amateur rally purposes. Are there are diffs that would be a straight swap? I appreciate any info i can get.
Thanks in advance!  

Hey all, i've got a bit of a different one (i think), i have an NA 2004 Blobeye impreza with SOHC, wanted to know if the DOHC heads would be compatible with the block i have? what kind of process would i need to go through to have this work? or would it just be a straight swap?

ALSO

Is it possible to put the intake manifold from a WRX or a WRX/STI from the same model onto my NA engine? (i have a full exhaust system from the headers to muffler and will be doing an intake soon too, and wanted to know if i could slap one of those red beauties on there)

Thanks in advance!