A schematic i am using asks for a LM7805, but all my suppliers have is a L7805CV. Looking at Data sheet i believe it is still ok to substitute? Couldn't see what the M and CV differences made?
Different manufacturers often use trailing letters with different meanings. This can be very confusing until you can find the datasheet from the manufacturer.
While datasheet search sites are handy, you should always go to the manufacturer's site to download their most current datasheets for the parts you're considering purchasing; you may discover that specifications have changed, the part has been discontinued, or there are better parts that you can substitute.
LM7805 provides 1A you can get a little more with good heat sink. Also thermal cutout and short circuit protect. Get both data sheets and compare depends what you making the regulator for to supply.