MackDaddy1150

I need help with 81 superliner to decipher engine serial number. All the dealer can say is it was factory 525 KTA. I am building this truck as a 5 axle super dump, bigger box, double drop axle, have a lot of parts ,quite cummins savy, but I have never owned a KT.. pushing for 800+hp. Just built new turbo, waiting for weather to clean up a little asphalt season is coming soon. Also need some help with interior such as floor mat, and some hood pieces. I own several Pete's. My first Mack. I've wanted this truck for over a decade and need Mack help.

So I have an 81 Superliner I'm building and it has no esn present. Mack dealer can't decipher anything aside from being speced with a 525 k19. Any ideas??