Adjustable boot springs were an item created as a retro fit. They were most likely made in an engineering or machine shop. I have a pair in my FC, and pulled one out so you could have a better look. This one was made as a one piece unit, with the center nut being part of the bolt itself.
Here is how they work:
The bolt obviously has several key features.
A slot for the spring. A hole in the end for split pin to hold spring on. A nut about half way down. Note that this nut is fairly thin, to allow the hinge to seat in alignment. Thread on one end to take the locking nut.
The bolt goes through the cars support in the place of the original spring pin, using a washer. This pin is easily removed with vice grips and a bit of muscle, should snap off leaving a neat hole the correct size. Next, the boot hinge goes on the pin. The hole in the hinge may need to be enlarged to fit. Slide the spring into the groove, ensuring the lug on the end is facing the right way. Insert split pin into hole in end. On the threaded end, throw on a couple of washers and a nut and tighten. To adjust, throw a spanner on the outer nut (spring side) and tighten up tension on the spring. Nip up the inside nut to lock in place. you may need to tighten or loosen as you check the boots movement. You should be able to get the adjustment so that the boot stays up in the half open position. I also use a second nut to lock the whole thing from moving, but I guess a spring washer would do.
This bolt could be made using a bolt and a few power tools at home. Cut the head off a bolt. Cut a groove into it. Drill a hole in the end. Cut a nut in half and weld half to the bolt. Use the other half as the locking nut. You would have to be carefull of weld placement to allow clearances etc. These pics should help someone reproduce the whole set up.
If you need a pic of the bolt in place or any further details, please ask.
Regards
Alex
Mine is showing a bit of wear, might need to hit it with the mig and fill that groove.
