I'm very concerned about the 1-1/4" bore being correct...that's the size used in the small trucks and I think with Tandem Axles you need a much larger bore to fill all of those wheel cylinders. It's hard to say what's been changed over the years, so what you have in hand may not be right either.
BTW, is your Tandem Axle factory installed or is it a after market "tag axle"?
The Truck Master Cylinder parts page is very confusing, so I took a photo so you could look it over and see if it helps! You need to confirm the Series...are you sure it's a C-60 and not a C-50 or C-80?
Mike B
