What should I do with my 340 that has been sitting for years.

Sedanman said

A wire wheel on a drill will knock most of that rust out but I would see if you can pop the crank out and leave the rods (with caps on) and pistons in the cylinders then push the pistons down and wire wheel the rust out and pop out the pistons. I have used a chunk of 2x4 and a sledge hammer to tap them out.

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That's what I would do. Remove the crank (if possible) or at least get it as loose as you can. Then get your dingle ball hone and hit all the cylinders as best you can. Then move each piston down as far as possible, since the majority of rust is usually on the top side they should move down pretty easily. Once you moved as many pistons to the bottom of the bore you can really get the hone in there. I always take my time and get the easiest piston out first. Then the second easiest and so on. If you take your time you'll be able to get the crank out and start working on the real stubborn pistons last.
Of course...soaking always helps!!

treblig