OK, so on my way to work I decided to wind out my new engine from a stoplight on the highway (385cu in SBC iron block, forged rods, crank, & pistons, 6500rpm redline, in 1974 'vette).  Apparently in winding it up to ~6000 RPM in 1st & 2nd, I threw my alternator/water pulley belt.  Within a couple miles I saw the water temperature pegged in redline at 280 degrees plus.  I took the next available exit, I believe within 5 miles of where I threw the belt, and pulled into an Autozone where I was able to slip the belt back on after about 45 minutes with the engine off.  I needed 2 gallons of antifreeze to refill the radiator, and I was able to start it back up without any difficulty and the water temperature appeared to be staying about 180 degrees for the rest of my trip to work, which is normal operating temperature for this new engine.  However, my concern is that I may have caused some damage running at such a high heat for even a few miles.  If anyone knows much about high-heat damage characteristics to engines, regarding sustained high heat over even a few miles, I would appreciate anything you could tell me, particularly if I should be OK or not...  

Okay, I was able to speak to my engine builder, and I appear to be in the clear thus far.  Basically what he told me is in a case like this, the first thing to blow would be the head gaskets, or the heads could've cracked (especially if I'd poured anything cool into the system right away, which luckily I did not).  As when I caught it and pulled over the engine was still boiling out the antifreeze for at least 10 minutes, and it only took a little over 2 gallon to refill it, I should've had enough coolant to prevent any major damage, probably losing between half to 1 gallon of the coolant while parked with the engine off alone.  I've since driven it at least 100 miles since my post yesterday morning and haven't noticed any ill effects, and the coolant and all other fluid levels are holding steady, so looks like I dodged a very large bullet.  I will however be replacing my belts this weekend, and having the alignment of all pulleys checked out so I can hopefully avoid anything like this in the future again.  

If you had cooked something in the motor after your overheat, ti would've been obvious fairly quick.

Easy way to tell, check all the plugs for any sign of water/coolant being burned in the combustion chamber. Second, check for signs of collant in the oil.

Since you boiled the engine pretty good, I'd change your oil as an extra precaution, since oil looses some of it's lubricating capabilties when it gets toasted in an engine overheat.