We installed one of AIT's B-Magic full Wide Body Silvia kits on a HB, it was before they had the 50mm HB rear, but I made the Coupes work. All of the kit fit pretty much perfrect, no problems at all. Most kits require some work, if it was entirely bolt-on no work neccesary, then they would charge dealer pricing. If anyone's wanting the kit or peices, we sell it here at our shop, give us a call for pricing 678 770 4516.
Here's a link to his car we just did with the kit
http://www.e-emotorsports.com/rb240.html
Eric
www.e-emotorsports.com