Looking in my factory assy manual it shows a 3600 with open driveline. I assume it is showing a 54 as it has a one piece open driveshaft. Seems like a long distance to span with a single shaft but that is what it shows. Anywho what you describe in your truck is the typical setup for a pre 54 3/4 ton. The 1 ton is different, it's a two peice open shaft.

I have the rear retainer for the sm420 you would need to run the open shaft and I am looking for the u-joint that would go on your setup between the sm-420 and the short closed shaft if you would like to trade. You would still need to find the shaft(s).


Grant
1950 Chevy 3100
1952 GMC 150 (In Pieces)
1968 Chevy K20
1966 Shovelhead
1978 BMW 100S