I'm still trying to tune my carb and I was told I should have somewhere from 18 to 24 inches of vacuum at manifold port. the most I'm getting is 7 inches at 1k rpm's 1/2 turn from seated. Setup is sb406, 10.0/1,comp292h .501" 292/292 144/144@50 110ls, holley750dp 4150, brodix ik200's, weiand xcellerator single plane. Any ideas? Thanks

Where's your timing?

11 degrees btdc base

You may have 24" vac going down hill but I doubt at idle. More like 12-16 and thats plenty. You cam and timing plays a part here. Try setting initial about 10-16* and see what happens. Need to know what your total is . Got dial back timing light?

At 13* initial it will "diesel" when I turn the car off. I have a dial back timing light but from what I hear, finding total advance will be innaccurate since I have an msd 6al.

A couple thoughts. I sure hope I don't talk 'down' to you. That said, here goes.
Your timing is close. How about vacuum leaks? Did you tighten the carb baseplate evenly? Did you make sure that ALL vacuum ports on the carb and manifold are connected or capped? Is your setup using vacuum advance? Is it connected to full time vacuum? The 11 degrees you quoted is a good base value. Vacuum advance is on top of that. Of course you still need more vacuum before it'll even kick-in. Still thinking,,,,,,

Edit; your last post beat me to it. Don't be setting your timing to the fact that your engine diesels (run-on) when you shut it off. That's a separate problem that really cool engines are prone too. It's caused because your throttle plates are open a lot to keep the car drivable. The cure is an idle solenoid. Then when you turn off the key the solenoid releases and the throttle plates are free to close to the final stops. Or you could install fuel injection.;)

I run a msd pro-billet dist. with mechanical advance. I'll check vacc. ports and I did tighten carb in sequence but maybe second times a charm.

That setup should pull 10-11" vacuum at 900 rpms easily enough. You need more initial timing, and you need to back off the idle speed screw. I'm guessing your probably getting very little response from the idle mix screws at this point. Jack up the initial timing to about 16*, limit total advance to 32* (400's don't like a lot of total timing, and those heads won't like a lot of total timing either, but the big cam and relatively mild compression will love a bunch of initial timing). You'll have to go thru the timing, idle speed screw, and idle mix screws a few times to get it nailed down. Raising the initial timing will increase the idle speed, so back off the idle speed screw and then re-adjust the idle mix screws, then repeat as necessary.
My 388 with the 294s comp cam solid (250@.050), with a 7530 weiand single plane intake and .020/.022" lash will pull 11" at 900 rpms. Switching to a 300-36 holley dual plane and loosening up the lash to .024/.026 put me up to almost 13" idle vac at 900 rpms. Power brakes with either setup was no problem. A similar sized hydraulic cam will pull a bit less vac at idle.