I seen a post many months ago from Boba, looks like DirecTV used 2 styles of 18" dishes, one with a Rectangle Tube and one with a D Tube. ALthough the DP LNBF will work on the DTV D Tube, the Rectangle Tube will need to be modified to use the DP LNBF.
I see the OP has several (technical) post in this forum.
That said, and assuming he can get 129 in CA, or 148 for non-HD channels, maybe he should consider the following:
(1) Peak the SuperDish for 110 & 119; then purchase a Dish 300 with DP Dual for either 61.5, 129, or 148.
(2) Get a Repoint Kit for the SuperDish which will give him 110/118.7/119, and add the 110 LNBF from the SuperDish for 129.
(3) Get a Dish 500 w/DP Twin for 110/119. Then reposition the SD-121 for either 61.5, 129, or 148, depending on what he is trying to receive.