OldIHC

Hi from the UK
I have just brought two metro,s
One a 59 and the other is a 58 shortwheel Base
Firstly are these vans 6v positive earth
And does any one have a good source for brake parts
Thanks

Are the original cables on the truck? The positive battery terminal is always bigger than the negative terminal. Which cable end has been opened up the farthest? That's battery positive. Most likely 6v battery positive was connected to the frame or other ground. Around here we've learned to add a new cable from battery ground to near starter on engine block, bypassing all those bad frame connections.
12v negative ground conversion is another story...
My '60 B-120 has identical front spindles, brake shoes / drum diameter as my R100 pickup. This is despite the B being "big six" wheel bolt pattern and the R being 5x4.5" pattern. Same front brake shoes. So I suspect these are fairly common (here, anyway) front brakes.
What bolt pattern is your truck?

By 1957, all IH trucks were 12 volt, negative ground. Probably a year or two or three earlier than that, but I know '57 was 12V, negative.

Axles/brakes,.....an axle swap (front & rear) to something more modern solves a multitude of problems with finding brake parts, wheels and suitable tires. .......one opinion......