That's what I'm getting from it too. Anytime you have a near stock stall converter and have the idle turned up to 1200 it'll naturally want to take right off. Shoot I've got a 3500 stall in mine and if I'd set the idle at 1200 it'd do 10-15 mph. Not saying the converter isn't bad, but it sure sounds more like a engine issue to me, most likely the carb is leaning way out either from a vacuum leak or obstruction somewhere in the idle circuit, or messed up tuning by the dyno operator. Most dyno operators know enough what their doing but when an engine is idling on a dyno with no load he might have set the a/f ratio too lean to work when installed in the car and in gear. When you drop a car in gear the a/f ratio goes leaner, possibly it's just too lean to idle good. When I tuned mine I had to set the a/f ratio at about 13.5 to 1 in neutral because it goes up to 14.2~14.4 to 1 when I drop it in gear. Any leaner than that and it don't idle good. First and simplest thing I'd try is backing out the idle mixture adjustments a 1/4~1/2 turn and see if that makes it better. If it gets better back them out a little more and see if it gets better again.
And *** D55 Dave said retarded initial timing can also make it idle sluggish/bad. In fact the initial timing should to be verified first before doing anything else including adjusting the carb like I recommended above.
