Hughes makes a good converter. The GM2500 converter will be a stock core 12" diameter converter with the impeller fins bent slightly negative to yield the higher stall speed. A 258mm (10.25") core could be built to yield a similar stall speed, less slippage driving away from a dead stop, and more efficient all around. The deep 1st gear ratio of the 700 will make a converter slip less anyway in that situation. A custom built converter will yield better driveability.