Hi kevint,I've found a company that list a disc brake conversion for your '56' The only downside is you will need to convert to 5 bolt wheels. I tried a link the other night,but as i'm a technophobe it might not work so here goes!http://www.mpbrakes.com/products/product-detail.cfm?product_id=443
I believe the part # is DB1753B
I hope this points you in the right direction good luck! thumbs_up

1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.