MSP430 instruction timing
The Family Reference Manual has timing info for various instruction starting on page 63. The number of cycles is not fixed for a certain instruction, it appears to be dependent on the mode used. Here is one of the tables from the manual, you can see most instructions take more than 1 cycle:

 

I haven't used an MSP4340, but I imagine there should be a tool available in the IDE to time your code and tell you how many cycles it takes to run. I'd try and find/use this first - if you can't, use the info in the manual and calculate manually. 

If you tell us more about the device that needs the data (part number, format, etc) then we may be able to suggest alternatives (e.g SPI peripheral?). It sounds like a tall order to achieve this speed using this method, and not particularly efficient if a peripheral/PLD can do it for you.
With the price/capability of uCs nowadays, needing to resort to stuff like this is usually a sign for me that I need to consider moving to a more capable uC (unless the quantities are such that it makes enough of a difference)