I don’t have the part number, there’s no markings on it but I’ve got a picture.
It’s 1/2” thick. The 1250 worked best with 93 main and .028 high speed jets @ 32 degrees. It’s surprising to see what spacers do. This reversion or shear plate worked like a damn on the Barton while a super sucker spacer sent it the other way.
I made a pass with the 505 in the Plymouth with this shear plate on top of a Super Victor intake, it didn’t change the time slip from the previous pass with a 4-hole 1/2” wood spacer. But having said that the air was getting worse so perhaps there was a touch.
Hope this helps.