how about an NV4500? I believe you will be looking for the dodge version, but the conversion may be rather expensive. Nobody makes a sbc bellhousing for the nv4500 that mounts to the frame like the original bellhousing, so an adapter plate will need to be used in front of the dodge NV4500. The pilot shaft on the dodge NV4500 is 1 inch longer than the pilot shaft on the gm NV4500 making this swap possible. This transmission should knock your rpms down to about 2300 at 70 mph. This tranny also has a granny low, but it isn't as low as the sm420, so there is a little bit of a loss in first gear, but a tremendous gain with 5th gear. You may find a transmission and a transfer case from a dodge and use them as a package, or find a 2wd transmission and move your transfer cas back to accomodate.
