Nice pic
There's a few reasons why they won't reproduce this bracket. It was used in Firebirds only and the small body sender units don't exist that fit them anymore. These were standardised so even the original part number brings up revised larger sender since the 80's.
Depending on where you found my pic, may have also shown that I modified one to fit. One was rebent from a damaged bracket and crush tube added, another was made up from exhaust pipe with flanges welded on. I forget which is currently installed.
The problems don't stop there. Intact extension tunes are rare, and the reproduction tube is too long, and that is to suit a stock sender. Add a standard sender and it's far too long. I also modified one of those.
This all came about when accessory brackets were revised, top hose moved, to look more like a Pontiac engine. On regular Olds, the oil sender pokes out the block front where the alternator now sits.
To aid your search, 77-79 Firebird and TA with Olds engines only, and must have the rally gauge option.