Yes, my last 347 had the new Probe pistons and the pin was not in the oil ring. It still ate about a half quart in-between oil changes, but I didn't feel that was too bad.

The reason for the dart block is this... The standard 302 is good for about 400hp at the flywheel. More can be had out of the block and a lot of people will tell you so. I ran about 465rwhp and 600rwtq on my 347 with a 175 shot. The block did fine and I never had any issues. However I had a great tune and that makes a huge difference. I have seen bad things happen to stock blocks, with only a small amount of detonation. What you really have to consider is this, you put a 4340 crank, h-beam rods, good pistons, and some machine work into a stock block, do you want to take the chance of having the block split and damage your internals? On my last setup, it was a cast crank, Probe I-beam, and Probe pistons. Cheap build and got the job done. However, I wanted more... By the time I added the cost of the new Eagle H-beams, JE, and Eagle crank, what was going to happen with more HP? Don't get me wrong, it did eat my savings! New block, special oil pan, freaking Cleveland mains, special cam bearings, freaking freeze plug issue, and several other things that has kept my car down for a lot longer than it should be. Will it be worth it.... I hope so!

So what did I learn.... and

What do you want with your car? If you plan on revving it out, I would say 331 because you don't have to deal with the added stress of the longer rods on the 347. If you are OK with 6500k max, get the 347 with the newer pistons.

BTW, this is all my person opinion, so take and leave what you want. I am not a pro, but I did sleep at a Holiday Inn Express once.