79 automatic would be a 403. And that is the exception to the rule. Bt far, the most common T/A to be found is a the 79 auto 403 cars. This, just going by personal experience, is also the lowest priced of the larger CID T/A's, selling basically in the same class as the 80/81 non-turbo 301 cars. I've had a few over the years, and a transplanted 455 in a 79 has always brought quite a bit over the stock 403. Same for the 80/81 non-turbo cars. As far as value, I don't think it makes a bit of difference on a 79 auto whether it has the original engine, or another 403 pricewise. A 400 Poncho or a 455 anything will increase the value. Just my opinion though.