I saw a post a while back where someone was asking about converting their condensor in to a large oil cooler. I don't recall what was decided. Could the A/C condensor handle the pressure? Are the ports the correct size? I assume there is an issue with this conversion otherwise you would hear more about it.
I just removed all my a/c stuff today and have to admit an oil cooler that size would be sweet!

 

I think the consensus was that the passages are too small. I agree a oil cooler that big would kick ***.