1973-1976 Drum Brake Knuckles

Its just the 73-76 drum brake knuckles that I am after casting number 3402738 (easy number to remember) I converted my 69 to the big bolt pattern discs about twenty five years ago but I now want to put the Viper conversion on so I need these knuckles
So if anyone can help me. Its a bit difficault getting hold of second hand bit in the Uk.
Thanks again Dave