I am in need of a motor for my 02 wrx I am looking for the ej20 only now I dont understand the difference between ej20 and ej20g but I found a motor on ebay calle ej20g came out of a JDM impreza gc8 can I get some info on this motor and would this be a good motor for me to go withhh ebay link http://cgi.ebay.com/ebaymotors/JDM-...TruckQ5fPartsQ5fAccessoriesQQsalenotsupported
Those are the oldschool WRX and STI motors from Japan. They're pretty bulletproof but you wont pass emissions and will have difficulty tuning them. The big plus is that they're dirt cheap but with the abundance of crashed WRXs over here you're just as well off picking up a used EJ205 that will be just as reliable and powerful as an EJ20G/K.
depends on what he uses for an ECU. there's no reason he couldn't use his stock ECU, and swap over the appropriate sensors (cam and crank) and coilpacks to the new motor.