Machine 360 crank to fit in a 340 main block

I think you remember correctly. The hardness depth is very shallow. It can be retreated, not a problem.

When the crank is cut down, the machinest will ask you some questions. What bearings is one of them. Take time with the machinest on this topic and walk through it slowly so you get to understanding it all well.

The 360 in a 340 block is the first stroker to the small block done in the early 70's. With the 3.58 stroke and a .030 340, you'll end up with a 372 cid engine. NICE!
(378 @ .060 over)