78 F-150 Stalling when changing gears help?

Okay I have 1978 Ford F-150 Custom with what I believe is a 390 with an auto transmission, and when I shift from park to drive after it is already warmed up it stalls. The only way to get it to drive is to give it gas while changing the gear, which I thought would be hard on the transmission so I only did it a few times. Could anybody give me suggestions I don't know too much else about the truck so I don't know how much else I can tell you.78 F-150 Stalling when changing gears help?
Yeah most likely it is a 351m or 400, they stopped putting 390 in them in 76, but you could have a 390 or 360 if someone put it in it the only way to tell is to get the numbers off the block and check it. Also if you get an Lmc truck magazine you can look up your Vin in the front of the book and it will tell you what your motor is and everything about your truck. Also if its stalling its probably one of these 8 things,

1. Carburetor idle speed incorrectly set

2. Carb fuel filter clogged and/or water in the fuel system

3. Choke improperly adjusted or sticking

4. Distributor components damp, damage to distributor cap, rotor etc.

5.Emission system components faulty( If you have any of these)

6.Faulty or incorrect spark plug gap or damaged plug wires

7.Vacuum leak at carb, intake manifold or vacumm hoses.

8. Valve Lash Incorrectly set78 F-150 Stalling when changing gears help?
Check the timing it could be out of time and/or the car could be idled too low,you may also want to check for a vacuum leak this is also a common reason for engines to stall in such a manner,for more info you could go to a local parts store and buy a Chilton or Haynes manuel that covers you truck,if you plan on keeping the truck it would come in handy.
first its probably a 351m or 400 second try checking your egr valve how long since it was tuned up also check cap rotor listen for vacuum leaks adjust your choke check your choke pull off

hope this helps
Once it is in gear, if you hit the brakes does the engine bog down or stall? If so, I would bet the torque converter is shot.