How close, is to close for rad fans to water pump pulley space

You got a couple of issues going against you here. Normally that 3 row would do a better job but;
1. You really need about 1" or more to create a decent suction affect with the shroud. In this case not only are you not getting any real vacuum effect.
2. you are blocking the air flow from getting through the rad when you are at speed.
3. dual 10" fans are VERY inefficient. In our tests, our dual 12" fans yielded 2800 cfm, our 16" fan 2500 cfm and dual 10" fans just 1400 cfm. Such a poor drop off in cfm that we abandoned the idea of 10" fans.

I understand you needed the dual fans to gain some space. In your case, I would consider going back to the small 2 row and if a slim 16-18" fan will fit, then cross your fingers it's enough volume.