The original shifter on the original column works just fine. Pop the quarter sized metal plug off the top of the shifter box, clean the grease away from the shifter arms where each has a 3/8" or so slot that the tang on the shifter rod fits into, have a helper hold the shift lever up so the tang is in the upper slot and tack with a welder. You can discard the lower lever that used to operate 2nd and high. Make up a rod to run from the shifter arm on the column to the selector arm on the automatic. I posted a picture at my site on Photobucket, it is the 3rd picture in the second row and the truck is a 52 on an S10 chassis. The all weather starter button on the adjustable bracket has the starter solenoid wire running through it so it just starts in park.
http://s32.photobucket.com/albums/d41/coilover/ I guess you know that your 51 had a solid steering shaft all the way from the gear box to the steering wheel. This has to be cut to the desired length and a bushing/bearing put in the bottom of the column tube.
