flipping 68 gmc leafspring setup?

[KoFFiNuPaLuNg]

hey guys. im new to this forum and this is my first oldskool. it a 67 chevy cab and frontend on a 68 gmc frame w/rear leafs. it has a 76 front suspension setup. the thing is, where can i find a flip kit for the rear leafs? can i use on from a 73-8 something? i cant seem to find one for my particular truck. front suspension no problem to find the necessary parts. what flip kits have you guys used to slam the rear of your trucks? thanks
llokin forward to building this project.