There are several firearms out there that don’t have the ability to be accessorized with lights and mounts like the AR15 and stock options are very limited. My favorite battle rifle is still the FNFAL and I have gotten MOA out of the gun with very little modification. Having a good mount and I would consider a mount that is welded on is extremely important with this rifle. The DSA SA58 has a very good track record for holding up if mounted properly and that means using loctite. There is also a lot of truth to not over torquing a screws with firearms because you will find out a few thousand rounds later that the screws are sheered off.
When it comes to stock options, your old G3 or FNFAL does have more options with Magpul. Magpul Accessories are now the number one gun accessories for AR15s but the Magpul PRS stock is a very good option for making your battle rifle a DMR gun. The battle rifle has seen a resurgence in use and sometimes going back to proven design and making improvements to its ability to be accessorized is the way to do it. The FAL has often been over looked compared to the M1A, but that argument has become less and less.