HOT ROD HAULER PT7 CAB & STEER AXLE IN PLACE. WHAT DIESEL ENGINE SHOULD WE USE?

I FINISHED THE MODIFICATIONS TO THE FRAME. SET THE AXLE BACK UNDER IT. GOT THE CAB IN PLACE. NOW I AM TRYING TO DECIDE WHAT ENGINE TO USE. THEN MY WIFE THROWS OUT A HUGE IDEA THAT WOULD CHANGE THE ENTIRE DIRECTION.