Dauntless All this talk is making me want to get mine back on the road. The more I think about it, the NA redblock seems like a great choice, especially for a SWB. They'll happily sit on 4000rpm all day as the factory gearing would dictate at highway speeds, with far better economy from multi point EFI and higher compression. The 1500rpm higher redline and additional power ~40hp would be useful too, and the torque output shouldn't blow up the original 4 speed gearbox.
https://cdn.ozvolvo.org/uploads/9TIZXKA46CG7/dscf7617-jpg.jpg
Ironically, this beauty is almost identical to my aforementioned $500 junkyard jewel from years ago. The roo-bar (bull bar over here) was a different shape, but I had to do a doubletake to make sure it wasn't an old photo of mine. That would be a great project truck for a redblock swap.