Putting in the new rad

Well, one bad thing about the early mustangs is cooling. It is hard to get a cheap radiator for a big power engine in a 65/66 like you can the later ones (just swap in a big block radiator for the 67+s, and you're good). Whatever you do, don't get the base model, spend an extra 20 bucks on a slightly better cooling one, and make sure you run a good shroud, water pump and thermostat. To protect yourself some more, don't bore out your engine unless absolutely necessary. That 4 row should be okay, though NPD says their "3+" row cools much better than their 4 row for 20 bucks more. Trust me, this is a time you'd wanna spring for that slightly better model. Might want to also run a complete mix of that "Wetter Water" coolant. Do everything you can, I suppose. Thats all I can think of outside springing for a custom Be Cool or Griffin super-radiator that will costs 5 times as much or more.

To put it in its not to hard. Drain the coolant (should be a bolt on the side of the engine for this, take it out and its sorta like draining oil, if I remember right). When thats done, carefully disconnect all the hoses (probably will be more coolant in them). Then bol the new one in and go. My dad and I swapped my new one in in only a few minutes. Unless you have a nasty color in the coolant in the engine I'm not sure I'd bother with getting every last drop out, but that is a question for the other guys.

edit: Check out NPDs 3+ radiator, its about 200, saves a little money over that 4 row (they also have that 4 row for 170, but they say the 3+ outcools it).. 805-654-0468 is the number of the store closest to you

Don't waste your money on a 4-row radiator. A 3-row is more than sufficient. I would definitely recommend an electric fan, which will be a very tight fit with a 4-row. Water-Wetter is an excellant product.

Be sure to flush the new radiator backwards and forwards before you put it in the car, just to make sure nothing was left behind in construction.

The actual swap is pretty easy, as explained above.