Car wants to die when stopping hard

Some things to try

Does your car act like it's flooded after it stalls out? If not, it sounds like a vacuum problem. If so, it could be the bowl vents sloshing fuel out. I'll continue assuming it's the vents sloshing since it is the most common problem.

A sure way to verify that the vents are sloshing fuel out is by removing your hood and air cleaner and watching the carb vents when you hit the brakes (or even scarier while you stomp the gas) - Or you could just pop the hood after it stalls and look for evidence of a lot of extra gas on the butterflies and all over the air intakes.

On a regular Holley you could run a length of hose from the front vent tube coming out of the float bowl to the aft one making an inverted U (effectively connecting the two vents) and then slice a vent hole into the top of the hose allowing it to vent. That way under hard acceleration or decel, the excess fuel would ride up the hose and not slosh into the air intakes. It looks like your carb doesn't have the same brass-colored vent tubes but maybe you might be able to adapt the idea.

Also, I recommend you check your floats to ensure they aren't leaking or "fuel-logged" causing them to float lower than they are supposed to.

If the fuel isn't at the right level with the floats adjusted all the way down and they are in good shape, you might need to do some bending on the float arms to get them into the proper adjustment range.

had the same problem once

after taking the car in to have the engine tuned several times, I finally switched from a carb with vacuum secondaries to one with mechanical secondaries and the problem was solved.