Try using wield_obj_critter function.
if (obj_is_carrying_obj_pid(dude_obj, 568) >=1 and (los==1)) then begin
add_obj_to_inven(dude_obj,head);
float_msg(dude_obj,mstr(200),8);
remove_pid_qty(dude_obj, 568, 1)
wield_obj_critter(dude_obj,head);
end else