are you mating this to wider fenders and quarters, or just to a standard body car?
The STi Sport Bumper (front only), like several guys here have, is for a narrow body car, but not sure if they sell it anymore, might be discontinued
Burn Up does both front and rear setup as does L'aunsport. Their stuff isn't cheap, but it is extremely well made. Rear, no matter who the maker, will require the JDM rear support (not sure if you can cut up the US spec one) and Im guessing the JDM spec plate support too
Thats the thing though. Im not completely sure who made the Widebody. I'll put some pictures when I get the opportunity and see if anyone can identify who made the kit.I'd ask whomever is making the fenders and quarters then, since the bumper will need to be sized to mate up to those. Otherwise you could be in for a whole heap of a mess and alot of extra work