1971 SS454 Big Block Radiator

Greetings,
I grew tired of surfing the many Chevelle parts suppliers and figured I would come to the source for great information.

I have a 1971 SS454 with the M22. I want to convert the original 3 core to a 4 core Desert Cooler. Who has the best pricing ? Also, looking at my 3 core fan shroud it does not look like a direct bolt in as many suggest. The shroud hugs the back of the core on the inlet side. This appears to be a result that the header tanks on the cap side is 3" deep and the inlet side 2 1/4" deep, hence the offset shroud design. I do not want to cut the factory shroud for proper fit.

Who has done this before. I thought this was going to be easy -
Thanks

I see many folks advertising isolators vs cushion kits for the radiators. Big difference in price. My question is whats the difference.