My Grand Prix was originally a 231 V6. I lucked out and came across a V8 Cutlass upper fan plate in a local wrecking yard, so I used that to install my 4-core Champion. However, the grooves in its stock rubber isolators (and the two bottom rubber isolators that came on my car) were not wide enough to fit over my fat new radiator. I spent a while in the garage with an exacto knife, snips and a pair of heavy duty scissors carving out all four pieces until they would accommodate the new radiator. After that, it dropped right into place as if it were OEM.
That's good to know i was thinking about how to make that all work. I have my stock upper fan plate still and I have one that came with the gbody parts radiator. One of them got to work. I may up the fan size too if I can make them fit.