Your wheels appear to be 'after market' wheels... You could take one off the car, turn the wheel over, and WASH it on the back very well.. MOST wheels are identified somehow on the backside. Take a good photo and if you can't identify them, maybe one of us can help you.
I'm unaware that buying 'dropped spindles' is going to help you on the 'offset due to disk brakes'. If so, I certainly do not see the relationship there.
There are disk brake kits (without the drop) which do not offset the wheel mounting surface. This is one here which has some good characteristics, although I haven't used it personally.
http://www.ebay.com/itm/1955-1956-19...item237ab70fed
Note: I would prefer to use 'factory GM' parts if possible when doing such upgrades, and there are some options for using 60's or 70's GM disk brake parts for the upgrade (although I cannot comment on any wheel offset introduced).