I added a hayden fan to the stock cooler, with a derale inline thermostat.
I originally replaced the rad with a Koyo but it was defective, not wanting to wait for a new one or do it all over again I put the stocker back in and went the above route.
No problem, with a 7" fan you might even be able to mount it behind the cooler as a puller fan which is more efficient.
How thick is it? I believe we have about 2" behind the stock cooler but can be increased with washers behind the cooler mounts.