We have the original boom too. Removing any of the fasteners is really hard.
They are all corroded in place (stainless versus aluminum). Some had corroded so badly there was no aluminum left in the thread and the screws could just fall out (which a couple did).
So, removing the boom end cap may be a challenge!
One last thing, with the internal outhaul, it’s important that any fasteners in the sides of the boom are kept short. The Previous Owner installed some fittings and the shipwrights used self tapping screws. Horrible idea. Snags the outhaul.