idleing fine but will not accelerate

I have a 1979 jeep cj7 with the in line 6 258 4.2L that will run great at idle and you can rev up in driveway but as soon as you put the vehicle into gear and try to drive it spits and sputters then dies out gasping but will start right back up I have already replaced the following items trying to solve this issue = fuel sending unit, fuel lines,fuel pump,fuel filter,remanufactured carburetor,ignition mod,ignition coil,spark plugs and wires, and  distributor with new cap and rotor I also have had the timing checked ANY SUGGESTIONS Please help!!  

Try looking for a vacuum leak.  

What transmission does it have?  

I had the same problem with my 77 304, only difference was I could go for a few miles before it stalled, then would not restart until it cooled down. I had used a rubber cap to cover a manifold vacuum and it had a break/tear that I could not see. Once I changed it out all was fine.  
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Dirty Deeds DunderJeep 77 CJ5 304

hows a guy check for vacuum leaks? besides hearing hissing noises...  

with the engine running spray carb cleaner or starting fluid where you think the leak is, if it revs up you have found it  
Using the gas your hybrid saves!!

Try checking for vacuum leaks around the throttle shaft of the carb. Often low-buck carb rebuilders skip putting a new bushing here since it requires machining.

Also check the timing. Make sure the vacuum and mechanical advance are working. Also check the plug wires for burns or cuts.

If it we mine my first steps would be to ditch the factory problematic ignition and carb with a Davis Unified Ignition and either a Weber carb or Howell fuel injection. Those two parts will turn it into a completely different Jeep. You won't even believe it's the same rig.