I forgot to ask, what length are the screws that you are using? I'm planning on doing what you recommended to me a while back, 2 yate loon fans and a shroud.
I used a Sharpie to mark the thread that was to be cut and used a pair of pliers that have the wire cutter and snapped off the heads at the mark so that the nuts remained and the head did not. Moved the nuts to the marked end and screwed them into the Rad one at a time. Once I was satisfied with the results I painted them satin black up to the Radiator threads.