I just put 3 X 1/2" washers on each lug as a temporary measure, so I could move the truck (& test the brakes! - WooHoo!!).
Those collectively are about 0.30" total, or a shade under 5/16"
That does actually get the inside lip of the wheel outside the caliper - but only barely. Could just about slide a business card between. I would not call it safe with that small margin however, especially with a floating caliper.
Also the webs had to be trimmed slightly as per this image - http://jbhardin-gallery.com/trucks/wheeltrim.jpg courtesy of cletis

I wish I had taken a picture of the inside of the wheel to caliper to share - maybe I'll get one & post it up later - it's always helpful to see an image of these things to get a feel for the problem.

Yes, the brakes actually work - only moved the truck back & forward about 20 yds but they already feel great - looking forward to getting out on road test.

'51 Chevy 3100 Truck - OEM 216 Engine; three speed column shift transmission
6 Bolt disc conversion with dual master/vacuum booster
12V alternator conversion.
235 engine in waiting grin