I've used a dual core full aluminum ebay radiator without any functional problems. It was a little crooked and only had a spot for 1 fan but it was not bad for $100.
My Miata has a huge Koyo all aluminum radiator and it works great. In cold weather the car won't get up to operating temp lol
Basically with ebay, it's gonna be really hit and miss. There was a definite difference in quality between the ebay and Koyo though, Koyo feels much more solid and the welding is much better.