I picked this up from a pawn shop earlier this week for 60 bux OTD...: ) ...  The action is very clean and hasn't seen many rounds, but has some pitting from rust on the receiver and bbl. No big deal, I plan on giving it a nice Norrell's refinish job and this Stock Set that is on sale for 30 bux (Thank's 4 the link Teknic ) .....

  My intent is to make this a Home Defence Worthy shotgun, or close to it.

1) Which bbl should I put on it ??   20" smooth w/remchoke & iron sights perhaps ?? (Ebay special or similar, trying to keep it cheap)

2) Are the components available to install Ghost Sights ?? Would this be a better alternative than standard iron sights on a 20" slug bbl ? (not so cheap and what bbl would I need ?)

3) It came with a steel tube extention, it does not have a "clamp" @ the end to hold it to the bbl to make it sturdy. Where can I get one ?

  What else am I missing that I should do/have ???

      I thank you Gentlemen in advance  :) ...

I prefer the 18 inch riot barrel

As for ghost rings brownells carries them as well as the magazine clamp.  

Well if you are good with a hacksaw you could cut the barrel your self, then refinish it. Or you could take it to a smith to do it. If you do it yourself make sure to cut it a lil more then 18".  Tha is what I had done to my lil black bitch.   U got one hell of a deal on that shotty If you want to use the mag ex. with that gun just cut the barrel the lenght of the tupe on the gun like this.

I may have a clamp in my box of junk. If I do you can have it.

If it was mine I'd just shorten the vent ribbed barrel even with the mag extension like M4-TUNA suggested.  Maybe a bit more, making sure the vent rib has one last support pillar before the end of the barrel.  Install a new bead (oversized or possibly tritium glow in the dark).  

Refinish the metal with Norrells, add a mag extension clamp for stability & be done with it.