MY dyno and ET slip, What do they tell you?
That convertor is 90% of the problem. An 11" convertor with that high a stall speed will slip like a son of a ***** in high gear. Get either one of the "en vogue" 9.5" units from Dynamic, PTC, or preferrably Ultimate or a "tight" 8" set to 3600. Get some taller tires.
And you still didnt answer or did I miss it... Chassis dyno or engine?