I removed the existing fan screws and put those through both the case and the fans. It's my preference to have the fans in a pull configuration for easy dust cleaning anyway.
As for the exact thread type, I'm not sure but the head shouldn't matter. Have you checked the manual? If you have some nuts lying around you can pull one of the screws out and see if it threads into one of the nuts. That will tell you the threads in the rad.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…
