Sorry Vic, I thought I'd replied re the drop tank. I was able to find one pic in a book a friend had. From what I could see, the tank appears to be the same as the early tank used on the P40. I've looked in my spares boxes, thinking I might still have a 1/48th scale P40 tank from which I could scale-out the dimensions, but no luck I'm afraid. I think it must have been in the 'big' spares box, with over thirty years worth of bits and pieces, which was lost in a house move following my divorce! Darn !
I reckon if you can get a P40 tank, the small dimensional differences won't be noticeable in 1/72nd scale.