318 Mopar vs. 340 Mopar

The 8 1/4 was used IIRC in performance cars after '72. I seem to recall seeing a couple 340 stick cars with 4.10SG 8 1/4s under tehm... In any event, the 7 1/4 wont last very long, even abusing it with a slant. Been there, done that... In terms of the differences, there are 22 cubic inches that are different if you rebuild both of them with performance in mind. Even with the smaller heads. No other difference really. I'd find a nice 318 core, stick some good pistons in it, and run a set of 308s on it with 1.88 valves. Cheap, easy, and will run with any equally built 340.