I have a shooter grade HK 91 in 308. It has marks in the finish from a port buffer and claw mount as well as insertion marks around the magazine well.
It has the wide forend with the provions to accept a bipod. It also has the butt stock extender. The mount is made by ARMS and is in good condition. One of the slots has been opened up slightly, but it doesn't seem to effect it's function.
Trades accepted on a Folsom style basis. It has to be priced well, and you have to determine what that price is. I'll not price your stuff out for you.