its easy tbh m8.
. the 24v has the same mounts as the 12v, pinto, Yb etc.
4x4 is not a problem either. the easyest thing to do is buy an xr4x4 as a donor car and use the interior, powersteering rack, mt75 gearbox+ v6 bell housing brakes etc and then u can weld the independant rear suspension on, which from experience makes a massive improvement. the front end of the p100 is the same as any other sierra.
u want a BOA, the BOB wiring is more complicated, BOA looks better, sounds better, and it starts as a better base for modification.