Hi Bad_Vision,
what are you going to do inside the frame? do you plan to treat it also?
I remember a thread about an acid-bath and hot-dip galvanizing for frames to protect the internal side also. I'm looking for the post about it but I can't find it. I've read houndred of threads in several forums last months, I can't remember the source.
Beside that, a guy who did a great job restoring his Hilux used for his frame some sort of marine antirust paint.
Take a look at this one:
'Mint' 405,000 km MK III Build Thread - Page 14 - Modifications - Hilux Pickup Owners Club & Online Community
he talks about that paint, Jotun Jotamastic 87, in the page 14.