That has to be the weirdest thing I have ever seen inside a boom. The pin itself is just a mounting the block, the rest I am guessing was used during installation
to get the block into the right place for the pin to go through. Personally I wouldn't even attempt to recreate that disaster.
I am not sure how much purchase
you are planning on, but I would probably go higher than the 4:1 that's there.
Reinstallation is going to be a bit tricky but isn't to bad.
1) get a piece of stainless rod the same size as the holes in the boom, and a little longer than the boom is wide. Drill a hole thru the rod on either end such that the holes are about 1/8" further apart than the boom is wide. This is going to be your new hard point.
2) run the bite of a doubled up line from the gooseneck down the boom out the back. A wire fish
helps a lot here if you have one handy, but just a weight can work.
3) put the bite into the D ring attached to the shackle
4) attach the rest of the outhaul
system and be prepared to insert it all into the boom.
5) using the doubled up line pull the block to the holes and then using a small piece of wire, screw drivers, or other tools to orient the shackle just above the boom, and slot the rod into place.
6) finally instal the second ring, and have a beer
. Getting that rod to slot into place deserves at least one maybe two.
Alternatively splice a piece of spectra to somewhere near the gooseneck and attach the block to the spectra. It's a lot easier.