Jimmy dies when put in drive or reverse

[SteedaLX]

I have a 1971 Jimmy 350 4brl. I just had the carburetor rebuilt and the guy tuned it for my truck. It has new plugs and wires. My truck starts up fine and idles with no problems; it also idles fine in neutral. If I drive it while the motor is cold it runs great; it feels very strong. Once it starts to warm up it goes to hell. If I pull up to a light or at a stop sign it will start missing and die. It will start back up fine but when I put it in drive or reverse it spudders and dies. If I happen to get it moving it will miss really bad, sputter and die. It is so wierd because if I come back the next day it will run fine for a while then do the same thing. Somebody said it could be the coil so I am going to replace it when I get home. Beside that does anybody have any other suggestions? I am going to take it back to the guy who does the motor work for me but I wanted to run through the basics before I took it in. Some also suggested I put an HEI distrubtor on it. Any help would be appreciated.