Thank You, dear Sir Taki.
Yes, it is Isuzu exactly. But it have some differencies from truck, shown below - in fenders, bonnet louvres and front grille:
Obviously, this is one of production versions, that depended of year of production.
Front grille looks like following trucks:
Yes, really - Japanese WW2 trucks (and their versions and modifications, in particular) are GREAT MYSTERY and ENIGMA until Today...