[Doug]

Just finishing up on making upper shock mounts for my leaf spring rear end 63 Lemans.
Using 3"x3"x1/4" box tubing I made up bolt-on "brackets" that fit onto the subframe rails with flat plates inside the trunk to bolt to. Springs are on 46" center-to-center.

Basically, a small hole about 1 1/2" square is cut into the bottom of the frame rail to allow the top eye and bushing of the shock to fit up into. The bracket is "U" shaped to straddle the frame rail and it has a 1 1/2" hole cut for the shock eye and bushing to fit in. The bracket is drilled for mounting bolts including 4 holes in the top, 2 for the shock mounting bolts and 2 for tying the bracket to the bottom of the frame rail. When mounted the bracket fits solidly up against the bottom of the frame rail and the top of the bracket sits flush against the flange of the frame rail at the top. To reinforce the tying of the frame rail to the bracket, a piece of 1/4" flat stock about 1" wide and about 1 3/4" long (width of inside frame rail) is placed inside the frame rail on each side of the hole in the rail.

As shown in the pics, the sides of the frame rails are not perpendicular to the floor pan so the brackets had to be cut at an angle to fit the rails. The sides of the brackets are "contoured" to fit. Final assembly will use 5/16" bolts with locknuts for mounting to the trunk floor and bottom of rail and 3'8" bolts with locknuts for the shock mount.