The only major modification you have to make when converting to JDM spec, is to remove the old USDM radiator support and have the JDM unit welded in its place.
no need to weld u can just bolt it on. a lot of people will tell you that u will get excessive body flex but i think they are anal. also if u dont want to weld theres a epoxy weld replacement that is actauuuly > than welding
mine bolted on with like 30 bolts(one for everyspot where there was a spot weld) and still going to weld it in the future. don't have any problems right now and it's daily driven