Slick 60's

I replaced my headgaskets last month and have been wrestling with this problem and would like some help.
352 FE with a cruis-a-matic
The truck runs and idles fine when in park, when you drive the truck, it runs great and runs better than ever at high rpm. When I come to a stop in gear the engine will stall. Even if I throw the trans in neutral when I am rolling to the stop, the motor will shut down, unless I hit the gas. I checked the carb and vacuum lines for leaks using carb cleaner and had nothing change. Tonight I will install a new fuel filter, but like I said, at sustained speeds it is fine so I am assuming the fuel pump is OK because it doesnt starve at high rpm. It has an edlebrock intake with a 2 barrel carb.

Please help me, could I have been one tooth off when putting the distributor in? could I have a vacuum leak where the intake manifold meets the heads?

You said it has an Edelbrock intake and a 2 barrel carb, is it the original carb? Did you remove a vacuum dashpot from the original setup? Some cars and trucks equipped with automatic transmission had them. It is there to prevent stalling in just the situation you describe.

This issue just came up after replacing the head gaskets. It ran great before, but I would imagine when I took off the manifold I could have done something to the carb.