My dad bought one last year during Black Friday for a really good price, like $600 good.
It has the 16" barrel, with what looks like a carbine gas length.
He wants to free float it and add an adjustable gas block.
The thing is, he is pretty frugal and is not interested in putting a bunch on money into the thing.
Can anybody recommend an inexpensive free float handguard and decent adjustable gas block for suppressed use?

If you want to put a suppressor on a CLGS 16" .308, you are going to have problems most likely.

You really want the gas port location, size, and barrel length all set up for shooting suppressed if possible.

For hand guards, it depends on which of the 3 DPMS LR-308 heights you have if you want continuous rail on top.

If you want really cheap, Guntec is an option:  Guntec