We have done a lot of testing on valve springs and have came up with the best performance valve spring for the 4.6L two valve and three valve engines. They will work with stock retainers or Anderson titanium retainers. good to 0.590 lift Valvesprings$297.80 www.realspeedauto.com Ph.631-563-7325 All parts listed are for the Ford Mustang unless otherwise noted. Copyright 2018 Realspeed Automotive Inc. All rights reserved.