how do i tell if my engine is

Under the head on the drivers side, on a flat milled area will be the assembly numbers. You will get limited information from this, but you will be able to determinte the build date, the displacement, and the year. If it's a 65 motor, the year will be stamped "A", if it's a 66 the year will be "B", if it's a 64 I don't think it will have a letter designation. The displacement should be stamped there as 273, and the build date will be the day and month. The casting date on the side of the block will narrow down the year also. This is all provided that it is an 8 cylinder car, if it's a 6, I don't know how to tell. good luck with your project, Geof