With a stock '74 318 you should be able to get a dead smooth idle at a low speed (~600 or so) & set the initial at 16 with the 1" strip of paper. You might shoot a blast of starting fluid in the idle mixture ports & check reluctor gap and spark plug condition on the starting. Is this a divorced choke in the intake? You might hold the coil wire 1/4" away from the intake while a helper cranks it with the key & see what the spark looks like.