The letters listed are for the car line and not just the model as is explained in your very own parts manual. P is Plymouth D is Dodge and C is Chrysler. This means all 383 4 barrel cars under that car line are subject to reference No.114. Now if only someone can decipher reference note 114 we would have the answer. Yes, I know that there is a reference to 2 Holley equipped Roadrunners up above with and without fresh air. Those are not mine because they have different reference numbers. If no one can answer that question about reference 114, I'll scan my chassis manual under the section about Carter AVS and Holley 4193A where it explains why certain cars came with Holleys and others with Carters.