Can a 318 crank and rods be used in a 340?

Ford seemed to do well with cast cranks. My 340 has a cast crank. Unless your putting boost, NO2, or 10K rpm clutch drops to it, a cast crank can live a happy life when balanced and all the clearances are correct.

The Scat I-Beams for $360 are a bargain if your rods need any work and the Scat's come with ARP bolts so add that $70 to the cost of your stock rod resize.

In the end, I'd like to see what the OP has in the 318 to start with.