tombaja

I just found out that my 2006 subaru baja 2.5 n/a with a 5 spd needs a new short block. I want to make it fast, I have many questions. Among them,what advice to you all have to give me, only looking for 300 whp at the moment, could i use the baja 5spd and a 2015 STI block? Also would there be any issues putting the 2006 SOHC heads on the 2015 STI then boosting it. Will all the the accessories bolt right on the STI block what do i need to replace for this? Could not find much online except for HOMEBREW subaru but was not sure what year STI block he had. FYI the STI short block my friend has for me is from 2015 and only has 26k miles on it with paperwork.