340 crank

Same crank as the 318. The only real thing to look for is if it is cast or forged steel. Pop one of the lobes with a small wrench and listen to the ring. Low its cast high its steel.
If it is in good shape it is worth a hundred bucks, if not maybe fifty. Turning it will cost around eighty or so. It seems like sombody says "340" and it is worth a mint, but you can interchange crank and rods without a problem. 273 and 318 are lighter rods than the 340. I built my 340 with stock 318 rods and have had excellent results.