100-400 USD
try e-gunpats.com
the 740 is a very old model, they sell for $250- $350 in this area
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.
The marksman model 740 is rated at 425 fps.
The 742 is a 740 semi auto with the feeding problems fixed. Made from mid 1950's until it was replaced with the 7400.
THE MARKSMAN MODEL 740 air rifle was introduce in1970. It was discontinue in 1977.
It will vary with caliber.
Impossible to answer without the sn or date codes.
100-400 USD
Call your local auto parts store for prices. Prices are different by store or state.
50-350 usd
Contact the maker for a replacement manual