Looks like it clears the crossmember to me:
http://www.vildinimotorsport.com/gallery/Gavin%20-%20SR240z/1.JPG
How much of a power-band advantage does the RB20 have, if any, over the SR's that it will make up for not only the extra weight it has over the SR but also the fact that with the SR in a Z you practically have a mid engined car so weight distribution and center of gravity are optimized with the SR vs the RB.