All I can tell you for sure is that the E0NN is 1980 or newer, and the C7NN is 1967 or newer.
Take a tape measure and measure the bore. If it's almost 4 1/2", it won't work on an earlier 5000 with 4.2" pistons. If it's closer to 4 1/4", then it *might* work. At that point you'll need to get out some more precise measuring tools to see if the block you have has been bored out or not. You'll also need to see if the pistons you have are standard or oversize.