1989 ext cab sas 302 swap help

What's up everyone? I've been busy since the last time I posted. Found some gems that I'll be sharing with everyone sometime soon. One of them is a 1986 extended cab, solid axle swapped running a Ford 302 5.0 HO. It's an automatic. Gorgeous build, I'll post some pics. I'm hoping to get some advice from someone who has experience with this. Engine runs great and shifts smooth but gets hot. The current radiator is the factory 4 cylinder one I believe. I put in a new 180 degree failsafe thermostat and burped the system. Stationary, at idle it will hold 185 but as soon as I drive it will jump to 200 to 210 pretty quickly. There is a 10 maybe 12" electric pusher fan in front of the current radiator, set to come on at 180ish.
So driving under normal load the temp rises, but at idle it drops back down. Couple ideas that I have are
1. Radiator isnt big enough to keep up.
2. Water pump blades are worn and causing turbulence at higher rpm thus no flow.
3. Combustion gas leaking into coolant under load. Head gasket actively failing.
Oil looks good, coolant looks clean, doesnt leak a drop and the truck doesnt smoke at all. I picked up a combustion gas tester yesterday. I'm going to start there. If that comes back good I was thinking of putting in a 3 core aluminum radiator from a 3.0 and seeing how that works.
Any ideas or suggestions?

 

Sounds like a bigger Rad would be the best solution.

 

I'm thinking so too. Any recommendations for a good aluminum 3 core for a v6?