Photoshop :: Blend Exposures

I have a bracketed series of a landscape shot from Rocky Mountain Park that varies by about 3-4 stops. In the lightest the shaded areas of the foreground are great but everything else, especially the sky and distant mountains, are blown out. In the darkest, the highlights are just right but the shadowed areas are far too dark.

The scans are from 6x7 Velvia chromes.

I have made a pretty good print by combining parts of three of the scans by cutting, pasting, and blending them. But there is a halo in one very difficult area and that's a very tedious project.

I have tried the HDR but Photoshop says the chromes don't have enough exposure range for HDR.