My favorite mod on our P-Pump build is the empty wallet mod.
LOTS of Engine machine work, Billet Rods, Forged Pistons, bedplate, internally balanced rotating assembly, ported heads, custom intake manifolds, jesel solid lifters, valve springs, roller rockers, custom dog bones, cam grind, pushrods, billet valve covers, billet front cover, timing gears, injectors, injector sleeves, injector hold downs, injection pump, pump hub, turbo, injector lines, ATI damper, belt drive fuel and oil pump, blow proof bell housing, 4 disc crower, reverser, drop box, Rockwell rear axle, tires, suspension, etc...
It is a HUGE undertaking. Figure spending $75,000 at least just to get it running down the track. Then figure another $25000 a year to keep it up. Those are figures of you building the entire truck with someone supplying you the parts. Figure another $35000-$50,000 for someone to build you the truck from scratch.
Those numbers are off the top of my head, but I'd say anyone that has ACTUALLY put one together would agree that they are pretty close to accurate. It seems like a good idea when you're thinking you want to do it, but the reality of the cost keeps many from achieving success.