My opinion: You are wasting time and money. SBP is just fine for most. They made millions of cars with SBP. For all the money you have spent, you could have bought a really nice set of SBP wheels and you could have moved on to something else.
I disagree, especially on a car that will see a lot of miles. 4 wheel drums are not adequate for modern driving. And KH disks have components that are not reproduced and are not always easily found in good condition. Even the SBP rear drums are not always available, there have been multiple occasions where the 10x1 3/4” drums could not be purchased for as long as a year.
The OP also said he wanted “wheel and tire selection”, which I assume means he wants something other than factory wheels or cragars, which is basically all you’ll get in SBP.
If you want to run 15” rally’s and don’t drive that much, SBP is fine. If you want to run a lot of miles (ie, wear out brake parts) and want to run 17/18” wheels and modern tires, SBP isn’t a good option.
