340 No low end power

My own feelings - like Cracked said - find out what cam's in it - you can get a good lead just by removing the valve cover and rockers from one side, and using a dial indicator on the edge of one of the lifters. Dio a compression test first, then pull the cover off... Once you know those two things post them and we can go from there. MP cams are easy to install way of which would give the symptoms you have. It may not be parts changing, but simple blueprinting that fixes it.