might be worth a shot. :thumbsup:
This may be as simple as your fans aren't strong enough. But there's only one way to find out for sure. You need more cfms. It's just a 305, not a built-up 400. You should be able to get enough cooling from a 4.0 sized radiator (and you do when more air is traveling past).
Also, make sure the hot air from inside the engine bay isn't recirculating to the front of the truck to get sucked back into the radiator. I remember the guys at extreme4x4 had that issue with a rear mounted rad on one of their projects.