I have an original hemi shaker base and adapter ring here. What's queer is the nut inserts for the shaker bubble, they are on the top of the ring and instead of being #10-24 they are for a 1/4"-20 bolt. The nut insert is the same as the one used on the 2 mounting feet on the bottom of the base.

Anyone?

Yes, it's common, my six pack cuda was the same way. Wasn't exactly condusive to keeping your Shaker Bubble crack free around the bolt holes.

I have one, actually two, but I was told they were a one day production mistake.

Just one example of why you can't always use blueprints and factory documentation as the "end all" to how these cars were built. Preproduction and running production changes (and mistakes) happened, never say never


BTW, the SPD of the car my example came on was 2/12/1970, LA car.

No arguing that tag Scott..it's a nice one.
I actually like the fact that the adapters with the top welded nuts make the scoop sit 1/4 inch higher

1/4-20 bolts on an unrestored 1970 Hemi Cuda

Original square nuts used by Fram on shaker assembly, 10-24 on the left, 1/4-20 on the right.
Adapter rings were supposed to receive seven 10-24 nuts spotwelded on the bottom as per factory blueprint.
The larger opening 1/4-20 nuts were for use on the 340, 440-6, and Hemi feet brackets.

from the print.

Barry, Dave's on the road and won't likely see this for a few days. I can only surmise that it relates to the Scheduled Production Date, and not the "Actual" production date.