Search "331 saga" in the Vintage Mustang section of this forum. Bad luck started by a short block bought from the Satan "AD Performance". Many factors come into play but the fact is if you bore a 0.030 over motor 0.030 over again and shove it out the door without even bothering to hone out the lifter bores bad things are going to happen. I could have at this point bought two 363's or whatever from Woody for what I have have in my current pile and it never fails to disappoint frequently.I voted for the 4.25 bore 347. I'm always torn on it, but, personally, that's what I think I would go with. 16 cubes is nothing to sneeze at but I like the idea of the big bore 347.
We may get to a point where there's no reason to ever not go with the 363. That time may be now as less and less people are messing with stock blocks and they're all the same price. Plus the rod ratio nonsense has proven to be just that.
Why has the 331 proven to be unreliable? Just bad luck?