Tom:
I'm not sure if this is what this conversation is about but I ended up modifying mine to make it fit my "Champion Cooling" 4 core rad. It is pretty rough but it works and I'm sure you could do a better job than me. I'm not that skilled with a cut off saw, so it came out "WAY" less than perfect. I also modified the rad support in similar fashion.
Also FYI, if you haven't bought the insulator pads, I previously bought a set of insulators for a stock 4-core rad, for a '70 Monte, and the short/top pieces did not sit properly on the after market aluminum 4-core. I ended up needing the 2 (stock) longer pieces that the rad sits on (bottom pieces). This is what allowed the rad and the "radiator top plate" to sit properly with the aftermarket rad. Hope this with the attached pictures makes sense.