Bill Thomas had his headers made by Douglass Manufacturing then he sold them to GM for the 67 Z's, and according to Bill he did not supply them in 68. That is why Kustom started making them for GM. Bill had two designs of the headers, the early version used a slip fit design collector like a race car, and then he went to the common 3-bolt flange style. The first design were sold in his catalaogs as "race" headers only, but there was a cone shaped adapter supplied with them to connect to the factory exhaust when ordered from GM. He listed those in his catalogs as #H536 for the Z-28 and road race applications. The other set with the flanges were sold as #H527 and used a 3-bolt flange adapter to connect to the headpipes. The ones Larry is reproducing are the first design and appear to be correct. The only notable difference is in the head flange as they are "cut" and not stamped like the originals, otherwise they are almost "dead-on".
The set of Stahl's are good headers, but the Hooker #2207 Super Comps fit great and breath just as well on a street Z. I installed them on a friends 67 that has manual steering, and they both went in from the top with no clearance issues. Then I put them on a loaded 68 with ps and a/c and had no clearance issues, but the driver's side had to be laying in the frame before the engine was set in to keep from getting them scratched or dinged up. Now they are close, really close on the driver's side at the steering box. The plus side is they are about half the price of the Stahl headers, and a grand less than the repro's from Larry. It is your choice................good luck.....RatPack....................
*** Jerry, Larry must be giving you a heckuva deal as they sell them for $1600 uncoated and and $1700.00 coated, and that is for the 67 BT version or the 68 Kustom version.