To Adjust the linkage you will need to remove the swivel from the Z bar and turn in/out to make your needed adjustment. If you look at the picture I posted, you can see that one end goes around the top part of the clevis pin where it goes through the fork. I have hooked the other end to the frame, but the spring rubs on the (KB) headers. To remedy this I made a small hole in the lip of the oil pan and hooked it there. That took care of the return spring angularity issue. The only issue is that you are space limited and need to drill the hole when the pan is out of the car or possibly use a dremel with a angle adapter.
The factory location for the return spring is the top of the Clevis as mentioned for 70. The 71 assembly shows a small attachment on the clutch fork. I think this is welded on so no one lost it. It should not be there unless 71 or maybe later as well. I am guessing to tighten up on the clutch the adjustment goes out. I would not trust the spring in the bottom of the clevis. I would think it was not strong enough. I have no problems with my spring hitting anything in the factory location but I was luck enough to find and NOS spring.
Jason, That is what the drawing in the assembly and service manuals show although the drawing is a little tough to see that end.
I have yet to assemble a Buick 455 4 spd car. I am looking at the set up and cannot see why you cannot use a full threaded rod in the rod end . Drill out the trunion large enough so that it slides on the threads (I used grade 8 all thread for this) and use 2 jamb nuts on each side of the trunion. All my MOPAR and Ford clutch rods were adjusted this way.
John, I think most guys would like to keep the threads in the trunion intact. Also the threads in the tie rod end are fine and trunion is course.
Here is diagram on how the 70 return spring attaches. The line goes to the top of the clutch fork and it appears the only place the hook could go is under the clevis head. It works fine.
Here is the 71 set up. The spring goes into a loop attached to the clutch fork. I have never seen one but it looks like it must be welded on. Also the clevis direction is reversed for some reason.
Clevis pin is reversed for southern hemisphere driving. Must be out of the Aussie version of the service manual.
Funny Brad, I would think it would fall out if the clip broke. At least the other way it may still stay in.
Dave my late build '70 has the spring provision, I thought they all did as there was no apparent place to attach without it. ou: DL
DL, If you look at the diagram from the assembly manual it looks like the spring attaches on top of clevis under the head. My clutch fork has no loop for the spring.
