Chimpy , i have heard the supra struts are a direct swap for the sc400 air suspention, just measured some in the garage, the bolt patterns for the top mounts are the same and the length is about the same. there is a company in the us reconditioning the rears and i heard also doing the fronts soon http://www.arnottindustries.com/parts_Lexus__LS-400__yid46.html
Regards
Lambo