Body is the same for 99%, but i thought the difference is in the USDM and JDM, for now i found via google only that is300 and is200 rear and front bumpers are different, for example:
trd lips for altezza will fit is200 perfectly and is300 with modifications. Side skirts should fit is200 and is300 with no problems i think. Thats why i created this topic to get an answer. Thank you Funky_Monkey for answer, I want to think that too, but we can be wrong at the same time