I have noticed similarities between Subarus and Nissans from working at both dealerships but my gut feeling is that a Subaru seat will not directly bolt into a Nissan, especially given the age difference between a classic SE-R and an STi. It seems reasonable to assume that some seat bracket adapters would be needed. This is just an assumption based on working on both brands. I have never tried to take a seat from one and put it in the other. I haven't heard of anyone attempting this either. Any halfway decent fabricator should be able to make something for you with no problems to make it work. I don't see it being much of a problem to make happen