KMJ roller rockers for 360

On the ebay ad it says that it can't be used on x and j heads "without extra clearancing". I'm guessing because of larger diameter springs? But they list these for the 318/340/360 with extra clearancing for larger springs:

http://www.ebay.com/itm/MOPAR-318-3...Parts_Accessories&vxp=mtr&hash=item4ceeabd942