Thanks again for all the replies!
So I'm gonna do some measuring today. I wanna see what the biggest Griffin I can fit would be without hanging down a foot. I think I'll do that, then I'd like to think about doing a different fan setup. Right now, I have a single 12 or 14" plastic flexalite fan, with a single electric fan up front.
Will I benefit more if I were able to squeeze in two puller fans out back with a shroud? The mechanical fan doesn't seem to do that much, and with the odd shaped radiator, it sticks up and down too much, that a shroud would have to be very complex to work. So I think if dual puller electric fans would work, that might be better.