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

Hi All,

I have a 1970 4 speed duster that I am restoring. It is an original 340 car but came with a 318 in it. So I picked up a 69 block that I am ready to use. My question is:

Can I use the crankshaft from the 69 318 engine in my 340? Also can I use the connecting rods. The 318 was running when I took it out.
If it can be used, do I have to get it balanced for the 340 engine.
Thanks for all your help.
Richie