That's about what I would have expected from Sanderson! You now have a couple options: Modern OEM exhaust manifolds are "tuned" to the engine, and flow as well or better than most general purpose "shorty or block hugger" aftermarket tubular headers. Granted they don't look or sound quite as cool, but if you have them ceramic coated it will improve the looks aspect. If you have a fair amount of building left, you could discuss a custom build with Sanderson and get on their list. Third option would be to either get Sanderson's "kit" option or one of their raw uncoated headers and modify it yourself.