Tom and David
I wanted to see when the TP cars in the 780575-780635 may have been restenciled as MP cars so I looked in my April 20, 1979 ORER. Not only were these cars still TP, but the next group, 780636-780674, were too. So, the Freight Car Journal 25 was in error showing these as MP cars. Looking further down the list these too were listed as MP in the FCJ 25 and were TP cars per the ORER in April 1979.
781000-781068
781100-781199
781200-781299

In defense of David Casdorph, a Joe D’Elia and Gene Semon who put the journal together, the Texas & Pacific, C&EI, M-I merged under the Missouri Pacific on October 15, 1976. I know some of the information they used to compile FCJ 25 were MP equipment diagrams so depending on the date of the drawing or corrections made to the drawings the cars in these series could well have been restenciled as MP and the drawings would have reflected this. The restenciling of freight cars was a ‘moving target’ and a TP car wouldn’t get restenciled MP until it was shopped for mechanical reasons on a rip track or car shop.