Starts idling rough when warmed up

I'm gonna take us back to when my barracuda was a 273 car. It would run fine until it reached what I would call operating temp. At this point it would start "bogging down" prompting me to put it in neutral at the lights, lights change, put it back in drive & she stalls, starts up right away and away you go, next lights same thing. Now move forward 2 years, I have a 340 in there, new carb, ignition, most things new but the same thing is the trans & convertor & I have the same problem. Is my convertor stalling to low when it gets to operating temp causing the engine to stall when I put it back in drive at the lights. I have held the brake on hard & revved the engine in drive and I believe the stall is around 1800. This is long winded so I will add some more later if you need me to.