It's a 71 motor that's already .40 over.
Not the best starting point for a stroker motor, or any rebuild for that matter. Get it sonic checked before buying any parts. Unless it checks out exceptionally thick (not something 340s are known for... quite the opposite actually) and/or cleans up with nothing more than honing, you'll probably want to start with a standard bore block. And if you go hunting for a block, STD 360s are far less expensive than 340s. Sleeving is another option, but that gets expensive quick.
Need to decide how fast you want to go. Generally consensus is that cast cranks and I-beam rods are fine up to 500 hp or better (assuming quality machine work, balancing and assembly).
Exception would be Eagle cast cranks. Lot's of documented issues.
CNC Motorsports has good deals on stroker kits. Unless you're building it yourself, consult with your machine shop.
