Both the same..heavy cast iron..4 spot calipers...and..as far as I know..after market light calipers like willwood are not available without making up special brackets.
However, If you win the pools you can get some CNC machined alloy calipers from UK...even get some 6 spots if you want overkill
http://www.ward-engineering.co.uk/calipers.htm
You all take care