The adapter I posted is on a car identical to mine. It's a late build L78 camaro with 456 gears.

I also mentioned my car has no adapter now but it may have been discarded, however the speedo is accurate.

There are a few different drive gears that mate with the driven gears. By Jody Haag's comments in threads, for a 4.56 rear ratio, the drive gear should be 6 teeth while the driven gear should be 20 teeth. This would eliminate an adapter. There are 2 different diameter drive gears also and corresponding driven. They must be matched.

Interesting thread here. Certainly not definitive, but educational.
https://www.camaros.net/threads/munc...o-gear.218963/

Interestingly, here is a page from the 1967 Camaro AIM dated April of 1967 (Note no revisions) which indicates the use of the 735 and 736 adapter after all. Note the use of 2 speedo cable clips with an adapter. Doug Perry's 69 L78 Camaro uses 2 speedo clips instead of 3. It would be very difficult to use the 3rd position speedo cable clip with the adapter. In my car the 3rd speedo clip dimple looks to have been pierced but never large enough to fit a speedo cable clip. It was instead filled with "dum dum" like material.

More information from a P&A catalog dated spring of 1967.

Here are the teeth counts and color based on speedometer driven gear part number.