I have a 12 valve p-pump its coming out of a box truck but its the same as the second gen engine. I was wondering what all mods can be done for around $1000-$1500 without getting into to many internals and how much power would i be looking at with it im not sure which hp motor this is

 

It all depends on the stock power rating and luck of the draw really, With just some tuning I got my 215hp truck to make 350hp and 800ft.lb. @ the wheels, motor had all stock factory parts on it only thing I put in it was a heavier clutch since after the tuning I could slip the stock clutch at will in 4th and 5th gear.

 

Here's a whole forum dedicated to your question. 98.5-02 24V P-Pump Conversion - Dodge Cummins Diesel Forum