Avoid the temptation of buying "cheap" and getting a two-row radiator. They're "cheap" for a reason, as is most junk. They won't cool a Model A engine in the upper part of Michigan in January during an ice storm - at midnight. Worthless, worthless, worthless! Maybe - and I mean a BIG maybe - a two-row radiator might have kept a Model A engine somewhat cool when the car was new and the passageways inside the engine block had not yet been coated with crud to reduce cooling ability. But 80 years later, even after boiling out the block, there will still be cooling problems.
J.C. Whitney used to offer the two-row radiator in the 1970's for a very reasonable price. I made the mistake of shopping with my wallet instead of my brains, and bought one. I couldn't keep my engine cool except during the winter, and even then it would occasionally boil over. There is nothing that will sour your overall Model A experience more than continually fighting a poor radiator and overheating. This is one area in restoring an antique car where one should not play it cheap. Bite the bullet and buy the absolute best radiator you can find, dimpled fins or not. That's only for show cars, anyway. You'll drive the car more than you will ever will show it. And a cheap-*ssed two-row radiator will be nothing but misery for you and your defenseless Model A.
Marshall