I purchased this used with the straight stock and a 28in. vent rib barrel. I have purchased a tactical barrel with rifle sights. Can I put a shell extension and or a pistol grip stock on this and be legal? I believe this is a pre-ban '89 gun.

If it's a pre-89 gun, you're already outside the realm of the usual arguments as 922r cannot and does not apply to firearms imported prior to its effecive date. But you're opening up a can of worms with that question, it's been asked here many times before.  You'll get vehement responses from both sides.

Many people believe this is a violation of 922r and arguing with them is pointless.  I could go into a diatribe about what the law says and why it is misinterpreted so much. but in the end, there are indisputible facts that basically speak for themselves:

1) Many thousands of Benellis have been imported and sold with pistol grips and mag extensions over the last 15+ years (since USC 922r was enacted) like the M1S90 Tactical, Defense and Practical models.  If they are importable that way, as they clearly are, 922r does not apply by definition.

2)  Not a single person has ever been legitimately hassled, let alone prosecuted for this unless it violated a state law.  And believe me, I've been looking exhaustively for such a person.  Neither the ATF nor NRA (or any other gun rights group) nor any federal court records have ever heard of such a person or situation.  I say "legitimately" because, while I don't know anyone in this category either, there will always be the uninformed police officer who might act on his uninformedness, but it won't result in a federal prosecution. If this is a violation of 922r, which is a felony prosecution, where is the prosecutory record of enforcement?  There just isn't one.

Adding a pistol grip and mag extension would put you in a population of people numbering in the thousands who have preceded you in doing so and have never had a legal issue about it.

Your state law, depending on where you loive may say otherwise, so check there, but federally speaking it's a non-issue.  This has been one of the bigger firearms-related internet myths out there.

Wanna make a deal on the straight stock?

IM me if you are interested.