yeah trust me I've been hearing about the block splitting scenarios for years and I know the issues. Let me see if I can share this link to this stock block vortech:
We installed just about everything but the kitchen sink on this one. Holley Efi, Trickflow heads, Anderson Ford camshaft, Systemax intake and then topped it off with a Vortech supercharger. The...
www.facebook.com
Now don't get me wrong I know there are concerns and the car above was a stock block build but not a stroker. With the 331 instead of 11-12 lbs like with my setup on my non stroked 302, I'll likely see around 6-8 but make more power. It seems keeping the rpms no more than around 5500-6k it should be fine. If I make 500 i'll be happy. If it's at 535 or so like that guy made I might be a little more nervous but I don't drive my cars crazy really and especially all the time. I baby them some but sometimes have to show some suckers who's showing off a thing or two lol.....
Because it's so close, I might think like you are and feed it fuel like it was going to make 600 and then just dial it back at the tuner.
I still don't know the answer to your 340 bracket question. I've never had to mount one. I am familiar with a return line, tank extension, that's supposed to cut down on aeration in the tank (bubbles).