Drive shaft u joint yolk

I recently installed a 8 3/4 third member from doctor diff. His 3rd members have the larger u joint yolk. My drive shaft has the smaller yolk. I used the adapter u joint also from dr diff but would really like to change my drive shaft yolk from the small to the large to match the third member. Does anyone have a source for the larger yolk. I tired dr diff but he must be extremely busy as I got no return call or email

Thanks