Like Jim said you can fab a thru mount idler support that mimics a 68-72 K-member idler mount. That said, all the fast ratio pitman and idlers I have seen have centerlink ball joint studs that point downward for 70-74 E-bodies. 63-66 A-body centerlinks have pitman and idler taper hole that only accept pitman and idlers studs that point upward. Here is a 63-66 Centerlink/pitman/idler setup Here is a B/E body with the fast ratio pitman and idler and the corresponding centerlink. Notice the stud bolts are showing from the bottom of the K-member. Where as in the picture above that bolts are not seen because they are on top. Here you can see the side profile of the fast ratio pitman and idler.