rickmg- Perhaps you should have checked your parts books, The front fenders for 1939-40 are all the same part number for 1/2t 3/4t and 1t. I know because I bought a 1tn fender from a vendor at a swap meet and was he mad when I told him it was for my 1/2 ton Suburban. He told me it would not fit, and I suggested he check his parts book. Was he ever MAD!
Perhaps you could find the vendor you saw and still make a deal.
599991 LH
599992 RH Stan