Thanks for the offers and suggestions. I have found a part number thanks for wdoftexas and the site
www.oldsmobility.com/10bolt-tech.htm The pinion shaft nut is GM part 3736464 and is a
7/8 x16 thread and is 1 1/8 across the flats.
I was also able to confirm the rear end is a 10 bolt first series for 55-64 GM and is a 3.9:1 ratio which I gather is pretty standard for the pickups. So my information that it was from a 58-59 chevy 1/2 ton seems correct as both the wheel cylinder number and front pinion bearing number check out as 58-59 1/2 ton rear end.
Jerry
