Congratulations!  These Westinghouse ovens are very cool-looking units!

For the power connection, these were usually wired directly to a supply line using both 115 volts and 230 volts, so you will need a three-wire cable that would be used for a range.   There should be some kind of a terminal block inside the oven, but you will have to remove the metal 'cabinet' that surrounds the oven.  You should see three wires leading to the terminal block: one red, one white, one black.  Connect your new cable exactly the same way (Red to Red, White to White, Black to Black).  The new cable could then be connected to a range power cord for testing.  NOTE: the white wire must be connected to the wire that runs to the center pin of the range power cord (it may be identified as the 'neutral' lead).    

Better still, if you can find a wiring diagram for the oven, follow it carefully.  It may still be on the rear of the oven somewhere.    Post photos if you have any questions before testing!