If it moves immediately, the cam is small not large. Big cams are notorious for poor torque off idle.
The "2400 stall" converter is rated with the Chevrolet 350 V8's torque at that RPM, far higher than yours, so your stall is less.
K = RPM ÷ (T^.5), K equals the engine speed at stall divided by the square root of the torque at that speed.
Estimating the V8 torque as about the displacement at 350 ft/lbs, the K value of this converter is about 130.
This applied as 200 ft/lbs to your L6 gives 1,800 stall with the same converter.
A looser (higher stall) converter will improve low speed response and acceleration, with some loss of mileage and increase in ATF temperature.
By comparison a "3500 stall" (with a 350) converter has a K value of about 175, which would stall about 2,500 with your engine.
I wouldn't change anything until you have enough miles on it to try WOT.
