Heres how I did this on an A body. Not much different to do really. I used an A833 linkage for a normal close ratio A833 for an A body I was working on. In your case you would need the Hurst linkage for 66-70 B body.
With the O/D setup, you have to mount the 3/4 shifter ear tab upside down. The 1/2 and reverse tabs and linkages you mount normally.
Put everything in neutral, install the rig pin in the Hurst tower, and install and adjust your reverse rod, and 1/2 rods. Now temp install your 3/4 rod on one end. Run the adjustment in about half way so you have adjustment either direction to fine tune it. You will notice it's going to be short by about 1.5" give or take.
You will have to cut and lengthen your 3/4 rod. How I did this on my A body was I found a spot on the 3/4 rod that was straight, I drew a lay line on it with a scribe, then cut it in half.
I measured the diameter of the rod, picked up a grade 8 steel bolt that had a shank long enough and with the same diameter as the rod i cut. Cut the head off the bolt, installed the section of shifter rod on the 3/4 shifter ear after cutting the rod and cut the shank of the bolt long enough to fill in the gap between the now cut in half shifter rod.
I ground both cut ends of the shifter rod to a 45° taper as well as both ends of the short bolt shank to a 45° taper. Using a piece of small steel C channel wrapped in aluminum tape as a jig, I clamped the rod with the piece of bolt shank in the middle. Lined up the lay lines, and tack welded the pieces together. Moved the L angle, reclamped and welded some more. I slowly built up the weld in the V notches on the rod stitching it together. Undid the clamps, removing the L angle, then ground the excess weld off the newly lengthened rod to make it look like it was always that length.
Remember an A833 O/D box is like a glass slipper. Its essentially a 1,2,4,O/D. The .6 O/D gear is in the 3rd gear spot. This is why the 3/4 tab is upside down. It's to keep the H pattern. 1,2,4 are left as a similar ratio to the close ratio 4 speed. You will have to really wind it out in 2nd gear, since the next gear in the H pattern is 4th at 1 to 1 ratio. Then into .6 overdrive. Aluminum case A833 trans it will not enjoy downshifting and loading the gears under hard throttle. Especially with a 440. Go easy on it unless you want to blow it up in short order
