by building a chopper you are well into the custom everything realm. some choppers like the occ's there are mounts and jackshft kits ready made for them. if its a super wide tire chopper your on your own.
i applaud your effort and know you'll learn along the way.
a chopper is never a good choice for a first build.
these kits were made to fit old 70's 10 speeds and they are a good choice for a first build, once you have learned all the pit falls of a first build on an old 10 speed the next build will be ez.