i wanna learn how to madify a cummins and other diesels

i am looking at getting a first gen cummins with the 12v engine. those cant be chiped they are mechanical not computerized so what can i do to make it fast lol. i like the chip cuz you can go from mileage to tow to performance and back and forth by the push of a button. is there any way to do anything like that to the older ones? where can i go to learn about it all lol? the diesel instructor has a 12 sec street first gen cummins. he wont really tell anyone what he did to it lol. so what kinda things would he of done or what would you do? the one i am looking at is auto 2wd ext cab long bed with single wheels on the back (no duely) thanks tyler