The RPM range and the torque band of the Diesel will be all wrong for the transmission and rear end gearing. The suspension system will have to be modified to handle the extra engine weight. You'll end up spending several times the cost of rebuilding the original engine and probably ending up with a poorly performing end result. Save yourself a lot of time, effort, and money, and sell the truck to someone who will fix it the right way.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!