Most of the top fuel cars now run tfx aluminum hemis, measuring 4.19 x 4.50, making 500 cubes including cumbustion chambers, and effectively consume about 1,500 cubic inches of air and fuel every 8 intake strokes. The tfx hemis have factory 426 head bolt, and main bolt patterns, and CAN be used with factory 426 type heads, and factory 426 cranks. They accept factory type cams as well, but not pushrods, since the cam is moved upwards about an an inch to accept the longer stroke. Chyrsler did pretty good first time around... i'd say.