Caliper confused.

[68racer]

Help!
I'm fitting a 70's front suspension clip to my '68.
Don't know exactly what year it came off as I never saw the truck.
Hoses run along the top of the top arm though. It has heavy duty discs, inch and a quarter.
Bought some recon calipers years ago and as I come to fit them they have 3/8 UNC threaded holes for the hollow hose bolt.
Trouble is the hoses have 7/16 holes in the end. The calipers on the clip have 7/16 UNF holes in them, can't use them as they are past it.
What's going on here? What year did they change the thread on the holes?
What year hoses do I have to ask for to get 3/8 holes? I want the hoses to run along the arm still.
I live in the UK and parts guys don't know this kind of thing, please help!
Neil.