Yes they are interchangable.
Check on ebay. You will find plenty of synthetic options and occasionly some wood sets. Most 7400 forearms and stocks will fit 742 models.
Yes, The receiver pins are the same as the Remington 870, so any stock that will fit the 870 will fit the 7400
Your local gun dealer can order (and fit) one for you.
try e-gunpats.com
NO
The Remington Model 740 semi-automatic rifle has long been out-of-production. You may be able to find an original stock on one of the firearms auction sites, like Auction Arms.com, or you might try ebay. Consider that the later model rifle stocks, like the 742, 7400 and 74 Express stocks will also fit, but will not match the 740 Model forearm pattern.
no
no
Probably not but call your local gunsmith
No, the Remington Model 1100 stock has a hole (recepticle) through the inside of the stock in the pistol grip area to accept the action spring tube. The Remington Model 870 stock has no need for this hole so the 870 stock will not fit on the Model 1100 action.
no there are some minor adjustments to the safety area
No