hey - google decoding ford part numbers... i found this Guide to Decoding Ford Part Numbers - ClassicMustang.com that basically indicates that you're main housing is a 71 *that's providing your DI is actually D1 instead* on the main housing and the other two numbers break down to 67 input and 66 top cover. My old one was a 79 *original to the truck I'm assuming* and I didn't get a picture of the new one but I know it's older now that I've read that. Hope it helps!