All 68-72 340 crankshafts were steel. Only the one year, 1973 was cast. You will hear people say the 318 steel cranks ain't the same yap yap yap.....but they are STEEL just like the early 340 cranks are ummm uhhh errr....STEEL. yeah, they might be a tad different, but completely interchangeable. with a good quality balance job and correct assembly, that 318 crankshaft will spin snot buckets of RPM, just like a 340 one will. You'll never know the difference. Likewise, if you're gonna build an engine 500 or less HP, a cast crank properly prepped will be all you'll ever need. I do agree though to stay away from big box auto parts stores. They suck when it comes to engine parts like cranks. There's nothing wrong with welding up a crank for repair. It's HOW it's done, and those mass produced "reman" crank shops ain't the place to get it done. Since all these cast steel cranks and such hit the market, the 340 stuff ain't the holy grail it once was. If somebody wants more than a couple hun for a good turnable 340 steel crank, they are stupid. Plain and simple.