looking for 4/6 drop flip kit

[sduckworth13]

I have a 1967 gmc 3/4 ton with leaf springs only in the rear ( no panhard bar or coils ). I am in the process of changing out the 3/4 ton suspension with a 5 lug disc/drum 1974 Chevy 1/2 truck suspension. I'm using my leaf springs from my 1967 GMC 3/4 ton, but using the 12 bolt rearend from the 1974 Chevy 1/2 ton. I called the famous ECE today and I spoke with a gentleman and told him that I was replacing my suspension using a 1974 Chevy 1/2 ton suspension and was doing a disc/drum conversion and I needed a rear flip kit for a 4/6 drop my 1967 GMC and he said that he didn't sell the rear flip kit I was needing for a 4/6 drop. I have seen lots of people post that they used ECE 4/6 drop flip kits on their 1967-1972 chevy/gmc trucks. Can someone please tell me the manufacturer that you went with and the part number I need. This picture is the underside of my 1967 GMC 3/4 ton
Thanks,
Scott