Well like I said it was an experiment and I guess they didn't like the results so they didn't even both with putting it on the lists.
If this is the case, and its that rare of an engine, how did your friends and family KNOW right off the bat what it was?
Term, seriously dude. I couldn't find word one about a 350 Big Block. Get a tape measure out and measure your engine. Compare your measurements to the chart. If they're close to the small block measurements, YOU HAVE A SMALL BLOCK, and you were misinformed by the people you know. If they're close to the big block measurements, you are correct about your engine, and you have something really cool. Now, if it IS a big block, I'm curious how you know that its a 350 and not a 366 or a 454, but thats another discussion entirely.
Seriously, take the measurements. There's no shame in being wrong, but if you can prove that you're right, then you have an even better conversation piece because you can show people its true.
Also, despite what you might think, that engine wont last long at those coolant temperatures. Try running the engine without a thermostat to see if the temperature goes down. If it doesn't, either your radiator is clogged, your water jackets are full of crap, or your water pump is on its way out. My guess is that its the radiator, but like I said, check your thermostat first. I know you said you changed your thermostat, but I've had brand new ones be bad before, so its worth double-checking.