I have written something wrong: the air tanks are not glued on the chassis but on the fuel tank! if I had done this, some screw holes would have been blocked!
So, now they are glued on the chassis with some pipes added:
On the 2 photos above, you can see the 2 screw holes at each end for the assembly under the chassis.
It lacks yet some other details: parts in order from PSC (fuel filler, gauge, etc...).
jpv in France