Weird Holley Carb Problem - Please Help

I have to Holley carbs, a 600 cfm C70F (67 GT 390 Carb) and a 735 cfm C90F (69 428 Carb). I have cleaned them both up, added a kit to them, and have different results. The 600 runs very well. However, when I put the 735 on my car, fuel spills out of the secondary chambers onto the secondary throttle plates. I have used the same fuel bowls to rule out float problems or anything to do with the fuel bowls, including adjusting the float level very low to avoid overspilling. I have rebuilt many Holleys but never seen this before. The car fires up without problem and has a high idle obviously, around 1200rpm or so. I have checked the gaskets and it is sealing properly around all of the venturis in the carb on the secondary metering block. The secondary throttle plates are closed properly so it isn't being drawn in on vacuum. It has 79 jets on that metering plate, 70 on the primary metering plate. Any ideas are greatly appreciated. Thanks in advance.

Both carbs have primary and secondary metering blocks with the stainless steel transfer tube between the two bowls. They are center hung floats. If it were too high fuel pressure, wouldn't that happen on the 600 cfm carb as well? If not, how do I correct it if that is what it is? Again, I have used the same fuel bowls for comparison. The metering blocks and core are the components I have switched out. Thanks for your help.