I would start my search at Smith and Wesson first.
Try CDNN, Samco, SOG, etc.
You buy a book that has the serial numbers in it.
You will need to buy or find a copy of the Standard Catalog of Smith and Wesson.
Try gun shops, gun shows, pawn shops, estate sales, garage sales, for sale ads.
You will have to buy a book.
Mossberg 1000 barrels will fit the Smith & Wesson 1000 Super 12 only !!
1973-74. Supica and Nahaus' Standard Catalog of Smith and Wesson is worth it's weight in gold (and it is very heavy) to anyone who thinks they may ever buy a S&W. also have serial numbers...
Call S&W and they will tell you. Buy the Standard Catalog of Smith and Wesson, 3rd ed by Supica and Nahas and look it up.
Try e-gunparts.com
suggest you buy a copy of the 'blue book' on gun prices (book store) and look up the model 60
Gun shop, gun shows, pawn shops, on line auctions, want ad, for sale ad, estate sale, garage sale, etc..