Mixture screw missing
 

Has anyone seen a Holley 4150 without the fuel mixture screws in the
rear metering block. not my carb, helping a friend.

http://gordonfrench.com/79-chevy/questions/carb1.png

Your missing a screw and the one in the middle is either a screw hole for the choke braket or the vacuum port for the choke. If its the port it needs to be blocked. To me it looks like the braket behind the choke lever is not on correctly.( slightly tilted upward in the rear

Are you saying the screws are missing, or the holes aren't even drilled and tapped? I've never seen a double pumper that didn't have metering block mixture screws.

The holes are not drilled an taped.
I'm wondering if it has the wrong metering block on it.

The threads will be deep. There may be a cork gasket hiding them. I would think that the fact its a "metering" block, it should have an idle mixture screw.

It isn't my carb, it belongs to a friend in another forum.
I had him use a mirror and said he could not see any threads.
Also took one of the screws out of the front and they would not fit.

Sounds like a defect. If it's a double pumper it should have a metering block, and if it has one it should have adjusting screws. On single pumpers they don't even put a metering block on the secondary bowl, regardless of whether it's a dual feed or single feed.

It is like 30 years old, so probably not defective.
Im thinking leave it alone, until he is ready to get a new carb.

I wish it was here, I would just pull the metering block off and look at it.

Even better; find an old Holley, pull the block off, and swap in another with screws.