I agree with Jim. I went with a 4 core standard radiator because the local vette guy was able to get me one at a great price. If I hadn't had that contact, I would definitely have gone with Dewitts.
I would strongly recommend a 4 core. Since I got the 4 core in mine, the temp goes up to 195, the thermostat opens, then the hottest it gets, even in traffic is 200.
Be sure to replace your hoses at this time and make sure you have a spring in the bottom hose. Might as well flush the block at thist time. Also, block fill the radiator. In other words, hook up the bottom hose, fill thru the opening in the block until it won't gravity feed any more into the radiator, then top off thru the radiator itself.
While you are this far, you could put in the cutoffs into the heater hoses to cut the heat down in your corkpit. They are gate valves for the 3/4 and 5/8 inch hoses that go to the heater box underneath the car. Makes it a great deal cooler in the summer time. I spliced mine in by the fender well.
Also, use the wife's turkey baster (might want to get her a new one) and draw all the fluid out of the overflow reservoir so that you get a new start to all fluid.
Finally, change out your thermostat.