Unfortunately, Norton, all those extra "Bells & Whistles" don't add to the value of gun.....and unless they came from the factory or were done by a nationally recognized gunsmith, can often detract from the value.
However, what I think what you may have is a factory Colt Series 70 Combat Gov't. Model. This was a forerunner to the Colt Combat Elite.
Assuming this to be the case, the Blue Book value is:
Series 70 Combat Gov't.
98% - $775
95% - $650
90% - $550
BTW.....from the serial #, your gun was manufactured in 1977.
Where to sell it? Well, don't
sell it to a gunshop.....you won't get nearly full value on it. However, many good gunshops will sell it on consigment for you.
However, to get full value, I'd suggest one of the gun Auction houses, such as ********* ( http://*********.com/
) or Auction Arms ( http://www.auctionarms.com/