If it's working I wouldn't worry about it. If you want the Armalite parts here is the link.
https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01&ReturnURL=/Armalite/Product-Category/AR10-Parts-Accessories/Lower-Receiver-Parts&Category=ac614400-ff09-4cdf-9d35-419a654e7201
A gunsmith is going to have to do a lot of the same things you can do. Take the rail off. That will eliminate anything touching the gas block or barrel. Set the magazine on a sand bag and shoot it at 25 yds or so.
Just change 1 thing at a time.
A gunsmith is going to have to take it to the range and shoot it too.
Does it still look good . Any corosion on the brass or bullets? I have had good luck w/ surplus ball ammo from the 70's & 80's. If it was stored in a dry place and not been exposed to real hot conditions it should be OK. YMMV
I have 3 FAL mags for sale. In good shape. 2 are Belgian. Small areas of surface rust on 2. These have been in storage for about 6 years. The darker one isn't Belgian. I sold both FAL's a few years ago and don't need these. There isn't any marks at all on the follower of the dark colored one.
$50 shipped.
Before you start drilling on things how about you put a few layers of duct tape on the face of the buffer and see it that solves the problem. If that works then you will know modifying the buffer tube is worth it.