David You can find any year four bolt valve cover head be it came from a 383 or the 413 and they will bolt on to your Imperial engine since they have the same part number. Starting with 1964 all 383's and 413's went to a six bolt valve cover head. Any set of this numbered head will bolt to your 1960 413 Imperial engine. Later in time the 413 was replaced by the 440. The early 440 head was the same part numbered head as the first series 413 six bolt head that showed up in '64. Any of these heads will also bolt up to your 1960 Imperial's 413. Then MoPar dropped the 383 and went to the 400 cubed engine. This means the 400 and the last models of the 440 heads up to 1978 will bolt up to your 1960 413 engine that goes to your Imperial. If it was my 1960 Imperial and the builder to be did not have the ability to seek this basic information I would go to some one that did. Watch this guy for he may not know the left side wheel studs have left threads. Rodger & Gabby Colo Spgs '47 De Soto Custom w/Fluid Drive & passenger door mounted swamp cooler '63 Le Baron w/F-Sweep trunk lid & std A/C '66 Le Baron w/dual A/C & reverbed AM/FM '70 Overlander - InterNational