A 4-row is only slightly better than 3, go this route only if you are desperate. A shutoff valve in the heater hose is probably more effective than that 4th row.
ETEL64, are you stuck on using a brass radiator? Understandable if the car is mostly original.
I've got a generic aluminum radiator from Summit and my 67 doesn't get hot with low-speed on a Taurus fan (I live in Houston too). My AC isn't currently charged, but even then with high speed on the fan, doubt it'll be an issue!
My vote would be for an aluminum radiator like Fluidyne or Griffen. The generic ones are just fine too. Alot of guys on the forums have them with good results.
I have a Fluidyne in mine and it keeps things cool with the AC on.
If you are set on keeping it looking original the get a good 3-4 row from one of the Mustang Shops. You might actually be able to get one from Advance, Orielly, A'zone etc with a lifetime warranty.
Ok, thanks folks for the recs. I went with a Champion (3) core AL CC339. Just came in and it is B-E-A-UTIFUL. Of course my next question is concerning a stock shroud. I have a (5) blade 17" fan. I have staggered in/out 1.50"dias. Anyone know where I can get a shroud?
I'd be willing to bet that if you were running the car without a shroud, that was 3/4 of your running hot problem. If the radiator you got was a direct replacement for the original you can order a new shroud from a local Mustang vendor, or a catalog. Go to Scott Drake - Home and do a dealer search. You might get lucky and a local dealer has one in stock. If not, I would be happy to order you one and ship it to you. The one for a 69 351 with a/c has a sugested retail for $72.50